
Class 
Book. 



CopyriglitlS 10 . 



- 



C0PXRIGHT DEPOSffi 



LECTURE-NOTES 

ON 

CHEMISTRY 

FOR 

DENTAL STUDENTS 



INCLUDING 

DENTAL CHEMISTRY OF ALLOYS, AMALGAMS, ETC. 
SUCH PORTIONS OF ORGANIC AND PHYSIOLOGICAL CHEMISTRY AS 

HAVE PRACTICAL BEARING ON THE SUBJECT OF DENTISTRY 

AN INORGANIC QUALITATIVE ANALYSIS WITH SPECIALLY ADAPTED 

BLOWPIPE AND MICROSCOPICAL TESTS, AND THE CHEMICAL 

EXAMINATION OF URINE AND SALIVA 

BY 

H. CARLTON SMITH, Ph.G. 

LECTURER ON PHYSIOLOGICAL AND DENTAL CHEMISTRY AT HARVARD UNIVERSITY 

DENTAL SCHOOL; HONORARY MEMBER OF AMERICAN ACADEMY OF DENTAL 

SCIENCE, 1906; OF THE METROPOLITAN SOCIETY OF MASSACHUSETTS 

STATE DENTAL ASSOCIATION, I907; OF HARVARD DENTAL 

ALUMNI, 1 9 IO; AND NORTHERN OHIO DENTAL 

ASSOCIATION, 191 2 

THIRD EDITION REVISED AND ENLARGED 
FIRST THOUSAND 



NEW YORK 

JOHN WILEY & SONS, Inc. 

London: CHAPMAN & HALL, Limited 

1917 



Copyright, 1906, 1912, 1917, 

BY 

H. CARLTON SMITH 



f 



j «• 



Stanbope ipress 

.GILSON COMPANY 
BOSTON. U.S.A. 



OCT 27 1917 



©CI.A476774 






PREFACE TO THIRD EDITION 

Three conditions are responsible for this third edition of a 
Dental Chemistry: first, the increasing demand for more 
thorough chemical education for dental students; second, the 
immense amount of new and valuable material constantly 
appearing as the result of physiological and dental research; 
and, third, the apparent demand for a book which shall be of 
general use to the dental profession aside from its usefulness as 
a classroom textbook. 

In the effort to increase the working value of the book some 
methods and many references have been included which would 
be unnecessary if it were designed for school use only. 

To facilitate the use of the book in other classes than my own, 
experiments have been grouped at the end in the belief that a 
selection may be more easily made from this arrangement than 
if they were scattered throughout the text. 

The outline character of previous editions has been maintained 
and the student is expected to have access to more complete 
works, such as those included in the following list, which is 
strongly recommended and to which frequent references have 
been made. 

Qualitative Analysis Stieglitz 

Qualitative Analysis Prescott and Johnson 

Dental Metallurgy Hepburn or Essig 

Organic Chemistry Norris 

Physiological Chemistry Hawk, Fifth Edition 

Metabolism Tibbies 

References have also been made to current dental litera- 
ture, not to bring the book strictly up to date, which is practi- 
cally impossible, but rather to teach the student how to study, 
which is a more important object of any course than mere 
familiarity with present day theories. 

H. C. S. 

iii 



TO THE STUDENT 

As the student of dentistry takes up the study of chemistry, 
it is necessary that he should realize that the course will be of 
value to him in the ability acquired to draw correct inferences 
from observed phenomena, and in the attainment of accuracy 
and delicacy in manipulation, fully as much as in amount of 
chemical knowledge obtained. In other words, he must do his 
own thinking, carry out his own processes and experiments, make 
his own analyses, or the time spent will be little better than 
wasted, for the chemical facts which he may happen to remem- 
ber will be of slight benefit in the work to which every student, 
worthy of the name, aspires, that of developing, broadening and 
elevating the profession which he has chosen as his own. 

The course of study outlined in this book is designed to 
furnish the starting-points, which will be of practical value in 
solving the problems constantly presenting themselves for con- 
sideration in the various branches of chemistry. It is hoped 
that these starting-points may, in the future, serve as the basis 
for work along the lines of original research and that the best 
interests of dental science may be furthered thereby. 

It is supposed that the student has had the advantage of a 
laboratory training in general chemistry and is conversant 
with the properties and methods of preparation of the so-called 
non-metallic elements, also with the fundamental principles 
and laws of theoretical and physical chemistry; that he is 
familiar with laboratory apparatus, such as test-tubes, beakers, 
crucibles, casseroles, evaporating-dishes, retorts, etc., and that 
he has had some experience in the ordinary processes of pre- 
cipitation, filtration, evaporation, distillation, sublimation, and 
crystallization. 



vi TO THE STUDENT 

If there is any feeling of insufficient preparation it is strongly- 
advised that a short course of preliminary study be taken. 
Chemistry furnishes the groundwork of all branches of medical 
science to a much greater extent than we are apt to think, 
and even in the study of subjects which in times past have 
been carried on with little reference to chemistry, we now see 
the desirability if not the necessity of a good general knowl- 
edge of chemical science. The physiologist and the bacteriolo- 
gist are to-day turning to chemistry for the ultimate solution 
of their most perplexing problems. 

H. C. S. 



DIRECTIONS FOR STUDY* 

These points carefully followed will enable you to get your 
lessons more easily, more quickly and to remember them longer 
than you otherwise would. 

(i) Let your lecture notes consist of a very complete, but 
very briefly stated, list of topics or subject headings concern- 
ing which the lecturer has spoken. Then copy and elaborate 
these topics before the next lecture. Use your topic list as a 
quiz sheet, asking yourself questions about each one. 

(2) Understand the topic — Do not try to remember any- 
thing you do not understand. It is a waste of energy and 
results are of no value to you. 

(3) Review often — If you can, study your lesson at two 
different times, that is, study at night and review it in the 
morning before going to class. Men who have studied the 
way in which the mind works, tell us this review helps one to 
remember. 

(4) Concentrate your attention, that is, keep your mind on 
your work, instead of allowing it to wander to the conversa- 
tion of others or to things happening within sight. 

* Taken in part from a sheet of directions by W. C. Crouch. 



TO THE STUDENT VU 

(5) Study away from interruption. Have a definite place 
for study where you will not be interrupted. 

Regularity of time for study also helps. 

(6) Recite and review again. Repeating what you know and 
reviewing, are the most important factors in mastering any 
subjects whether a rule in mathematics, a topic in history, or a 
principle in science. It is a good plan to review hard topics 
from week to week. 



TABLE OF CONTENTS 

Page 

Title Page i 

Preface to Third Edition iii 

To the Student v 

PART I. 
SALTS OF THE METALS AND QUALITATIVE ANALYSIS. 

Chapter 

I. Introduction i 

II. Metals and Their Salts 15 

III. Salts of Group One Metals 18 

Analysis of Group One 24 

IV. Salts of Group Two Metals 26 

Special Tests for Arsenic 34 

Analysis of Group Two 47 

V. Salts of Group Three Metals 53 

Analysis of Group Three 58 

VI. Salts of Group Four Metals 61 

Analysis of Group Four 66 

VII. Salts of Group Five Metals 69 

Analysis of Group Five 75 

VIII. Salts of Group Six Metals 78 

Outline Scheme for Analysis 90 

IX. Analytical Reactions of the Acids 91 

X. Analysis in the Dry Way 102 

PART II. 

DENTAL METALLURGY. 

XL Properties of the Metals in 

XII. Alloys 114 

XIII. Amalgams 119 

XIV. Fusible Metals and Solders 128 

XV. Dental Cements 135 

XVI. Recovery of Residue 141 

ix 



: TABLE OF CONTENTS 

PART III. 

VOLUMETRIC ANALYSIS. 

Chapter Page 

XVII. Standard Solutions 143 

Quantitative Analysis of Dental Alloys 166 

PART IV. 

MICROCHEMICAL ANALYSIS. 

XVIII. Methods 168 

XIX. Local Anesthetics and Antiseptics 173 

XX. Teeth and Tartar 189 

PART V. 

ORGANIC CHEMISTRY. 

XXI. The Hydrocarbons and Substitution Products 193 

XXII. Alcohols 205 

XXIII. Ethers 211 

XXIV. Organic Acids 216 

XXV. Cyanogen Compounds. Sulphur Compounds 228 

XXVI. Amines or Substituted Ammonias 233 

XXVII. Urea and Uric Acid 237 

XXVIII. Closed Chain Hydrocarbons 244 

PART VI. 

PHYSIOLOGICAL CHEMISTRY. 

XXIX. Ferments or Enzymes 256 

XXX. Carbohydrates 259 

XXXI. Fats and Oils 265 

XXXII. Proteins 269 

Simple Proteins 275 

Conjugated Proteins 280 

Derived Proteins 284 

Blood and Muscle 286 



PART VII. 
DIGESTION. 

XXXIII. Properties and Constituents of Saliva 291 

XXXIV. Analysis of Saliva 304 

Crystals from Dialyzed Saliva 316 

Tests for Abnormal Constituents 317 



TABLE OF CONTENTS 
Chapter 

XXXV. Gastric Digestion 

XXXVI. Pancreatic Digestion and Bile 



XI 

Page 
319 

321 



PART VIII. 

URINE. 

XXXVII. Physical Properties of Urine 326 

XXXVIII. Normal Constituents 331 

XXXIX. Abnormal Constituents 343 

Urinary Sediments 353 

Recording Results 358 



PART IX. 

METABOLISM. 

XL. Metabolism 361 

Experiments 367 

Appendix — Reagents 424 

Appendix — Organic Preparations 430 



DENTAL CHEMISTRY. 



PART I. 

SALTS OF THE METALS AND QUALITATIVE ANALYSIS. 



CHAPTER I. 

INTRODUCTION. 

Every science has a language peculiar to itself, a thorough 
understanding of which is an essential preliminary to the study of 
that science. Hence, before we take up the study of Dental 
Chemistry, it will be well to review a few definitions and perhaps 
a few of the facts of Physics which are closely related to our 
subject. 

Definitions. 

Matter has been divided into masses, molecules, atoms and 
electrons, and we are to study first the properties of these di- 
visions. For purposes of present definitions it may be necessary 
only to consider that aggregations of electrons constitute atoms; 
groups of atoms make up the molecules; and numbers of mole- 
cules held together by the physical force of cohesion form masses. 
The properties of these divisions of matter will constitute our 
further definition. 

The mass is any quantity of matter which has appreciable 
weight. It is influenced by such general physical laws as gravi- 
tation and adhesion. 



2 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

The molecule has been denned as the smallest particle of 
matter that can exist and retain the properties of the original 
substance, or the smallest particle of matter into which a sub- 
stance can be divided by physical means. This however gives 
us no picture of the molecule. To obtain this we must consider 
the facts of molecular weight, of molecular motion, of intermolec- 
ular space and of the effects of heat and cold; then we may be 
able to see the reasons for some of the things we have already 
learned about the behavior of chemical substances. 

The atoms we will consider as the smallest particles of which 
the molecule is composed. Our imagination should invest the 
atoms with all the properties of the molecule, but should in- 
clude some important differences. First: the molecules of a 
mass are supposed to be all exactly alike in composition. Second : 
they are attracted to one another in the same way and to the 
same degree. Third: their separation from one another does 
not of necessity involve disturbance of the electrical equilibrium 
of the mass. The atoms in the molecule are usually (not al- 
ways) of different kinds. They are held together by a peculiar 
force of selective attraction formerly called chemism or chemical 
affinity; and electrically considered the uncombined atom is 
supposed to be either positive or negative. 

The electrons are the infinitesimal particles of which the 
atoms are composed and have been regarded as constituting 
the force which determines their character. Professor Harry 
C. Jones says the electrons are negative charges of electricity, 
and explains their role in the theory of dissociation as follows: 
" Take a salt like potassium chloride. When it is thrown 
into water an electron passes from the potassium over to the 
chlorine. The chlorine having received an additional electron 
thus becomes charged negatively, while the potassium having 
lost an electron becomes charged positively. If we are dealing 
with bivalent ions we have simply a transfer of two electrons. 
Take barium chloride. The barium loses two electrons, one to 



INTRODUCTION 3 

each of the chlorines; the latter becoming charged negatively, 
while the barium has, consequently, two positive charges upon 
it." The mental picture may be difficult but it is very necessary. 

Ions. — The electrically charged particles or parts of mole- 
cules capable of attraction to either cathode or anode in the 
process of electrolysis have been called " ions " (Faraday's 
definition) . Ions may consist of single atoms as in H+Cl - or of 
groups of atoms (radicals) as in water H+(OH)~ or ammonium 
hydrate (NH^OH)". 

The molecule of an element consists of but one kind of atoms. 

The molecule of a compound consists of two or more elements 
chemically combined. 

Symbols. — Symbols are used to designate the various ele- 
ments. In some cases the initial letter of the element alone is 
used, as C for carbon. In other cases there is added a distinc- 
tive small letter of the name when there happen to be a number 
of elements with names beginning with the same letter such as 
Calcium, Ca; Cobalt, Co; Copper, Cu; etc. 

Chemical Formula. — A chemical formula represents the 
molecule and is made up of the symbols of the several con- 
stituent elements. Chemical formulae may be empirical, dua- 
listic or graphic. The empirical formula represents the molecule 
without reference in any way to its structure, i.e., H 2 S0 4 . 

The dualistic formula indicates compounds which may enter 
into the composition of a molecule. By this sort of formula 
sulphuric acid would be represented by H 2 O.S0 3 . 

The graphic formula attempts to show the probable relation 
of the atoms in the molecule by means of bonds, e.g., 

H-0 Ng ,0 

Valence. — Valence is a property of atoms and represents 
their combining power relative to hydrogen measured, perhaps, 
by loss or gain of electrons. Valence is not always constant for 



4 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

the same elements; for example, sulphur has a combining power 
of six in sulphuric acid, of four in sulphur dioxide and of two 
in- hydrogen sulphide. Nitrogen has a combining power of 
three in ammonia gas and five in ammonium chloride. Valence 
has also been indicated by the terms quantivalence and atomicity. 

Acid. — An acid is a compound capable of producing upon 
ionization positive hydrogen ions which may be replaced by a 
metallic element or radical. The more common acids are sour 
to the taste and act in characteristic manner upon a number of 
color compounds known as indicators. 

Base. — A base is a substance capable of producing, upon 
ionization, negative hydroxyl ions which may be replaced by 
acid radicals. Bases in general characteristics oppose acids. 
The strongest bases are known as alkalies, e.g., KOH, NaOH. 

A Salt. — A salt is a substance produced by the chemical 
union of an acid and a base. 

In the formation of the salt the acid may not have been 
completely neutralized by the base and an acid salt results. In 
such a case the salt contains a part of the hydrogen ions of the 
acid, e.g., potassium acid sulphate, KHS0 4 , the production of 
which may be represented by the equation 

KOH + H2SO4 = KHSO4 + H 2 0. 

Acid salts may or may not have acid properties such as sour 
taste and power to give acid reactions with indicators, for ex- 
ample NaHC0 3 , chemically an acid salt, is alkaline to litmus and 
has other physical properties of the bases. This fact is explained 
by the hydrolysis of the salt, hydrolysis being the utilization of 
the ionized water molecule. The condition may be represented 
as follows: 

NaHC0 3 ^ Na+ + HCO" 

H 2 *=> OH~ + H+ 

it IT 

NaOH H2CO3. 



INTRODUCTION 5 

If the acid is exactly neutralized by the base, neutral salts 
result. 

2 NaOH + H2SO4 = Na 2 S0 4 + 2 H 2 0. 

A salt may on the other hand be basic and contain a portion of 
the hydroxyl ions (or sometimes oxygen atoms) of the base. 

Example: Bi(OH) 3 + 2 HN0 3 = BiOH(N0 3 ) 2 + 2 H 2 or 
BiCl 3 + H 2 = BiOCl + 2 HC1. 

Reactions between chemical substances may be " completed " 
or " reversible." 

A completed reaction is one which progresses in a definite 
way irrespective of changes in temperature of the quantities 
of the reacting substances; or, a completed reaction is one in 
which one of the products is chemically inactive. This inac- 
tivity may be due to one of several causes, such as the production 
of an insoluble precipitate; e.g., AgCl in the reaction, 

AgN0 3 + NaCl = AgCl + NaN0 3 , 

or the escape of the product as a gas and its consequent removal 
from solution — as when carbonates are dissolved by acid. 

The reversible reaction is one in which the products remain 
to a greater or less degree in solution and a change of temperature 
or increase in quantity of one of the products may start a reverse 
reaction; for example, at the body temperature, dibasic sodium 
phosphate and uric acid may become monobasic sodium phos- 
phate and acid sodium urate, 

Na 2 HP0 4 + H 2 U = NaH 2 P0 4 + NaHU, 

while at reduced temperature, 

NaH 2 P0 4 + NaHU = Na 2 HP0 4 + H 2 U. (See page 242.) 

Reversible reactions are expressed by use of the sign *±; 
thus, MgCl 2 + 2 NH40H^ Mg(OH) 2 + 2 NH4CI. The reac- 
tion may be expressed as an equation if we know what substances 
take part in the reaction and what products are formed. The 



6 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

above reaction can be balanced at a glance and is therefore not 
well suited for illustration but the use of a little more complex 
equation will show how easily it can be balanced by a few al- 
gebraic combinations. 

Cu + HN0 3 = Cu(N0 3 ) 2 + NO + H 2 0. 
Represent all these as unknown quantities. 

x Cu + y HNO3 = z Cu(N0 3 ) 2 + m NO + p H 2 0, 
then 

x Cu = z Cu 1 x = z . (1) 

or y = 2 p (2) 



yH = pU 2 

yN =z(N) 2 + wN 

y 3 = z (0 3 ) 2 + m O + p O 



y = 2 z -\- m (3) 

$y = 6z + in + p (4) 



multiplying equation 3by3,3;y = 6js + 3m (5) 

and by elimination (4 and 5), 2 m = p (6) 

and 4 m = 2 p, then by eq. 2, y = 4 m (7) 

assuming that w = i, then, in7,y = 4; in 6, p = 2; in 3, 20 =3, 
or z = 1 J, in 1, x = ij. Knowing that all equations must be 
expressed by whole numbers we double these values and have 

* = 3> y = 8 > z = 3> m = 2 , P = 4- 

Upon substituting these values we shall find that the equation 
" balances." 

Theoretical Considerations.* 

In order to understand the phenomena of solution and precip- 
itation it will be necessary to include in our review a few of the 
terms of theoretical chemistry such as Phase — Physical Equi- 
librium — Mass Action — Chemical Equilibrium — Ionization. 

The term Phase refers to the condition in which a substance 
exists: solid, gaseous, liquid, crystalline. So sulphur is said to 
exist in four phases, water in three. 

The term Equilibrium conveys the idea of equality between 

* It is usually desirable that the study of this chapter be accompanied by 
very thorough lecture room explanations and laboratory demonstration. See 
page 367. 



INTRODUCTION 7 

opposing forces resulting in stability, e.g., the water in a closed 
bottle tends to evaporate; the tension or pressure of the vapor 
tends to prevent evaporation. When the one force equals 
the other equilibrium results. Another example, illustrating 
the meaning of physical equilibrium and at the same time 
showing why concentration is so often useful in producing pre- 
cipitates which may be easily filtered, is given by Stieglitz * as 
follows: " If a crystalline precipitate is in contact with a solvent, 
e.g., if barium sulphate is in contact with the liquid from which 
it has been precipitated, then this liquid must be continually 
in a state of change, not of equilibrium, with respect to the 
solution and the deposited barium sulphate. The more minute 
crystals, being a little more soluble than the larger ones, will 
supersaturate the solution in respect to the larger crystals and 
the excess will be deposited on these larger crystals and make 
them grow still larger. This deposition will make the solution 
unsaturated with respect to the smaller crystals and more of 
these will dissolve. The process is obviously a continuous one, 
and must lead in time to the disappearance of the minute crystals 
and the growth of the larger ones." 

Ionization has been defined on page 3, but a further con- 
sideration of the subject is necessary if we would understand its 
effect on chemical reaction. The following important facts have 
been demonstrated regarding the theory. 

The dissociated ions of the molecule are capable of migration 
and will collect at the poles of a battery according to the well- 
known laws of magnetic attraction: the positive ion (cation, 
or metal ion) going to the negative pole, while the negative ion 
(anion, or acid ion) goes to the positive pole. 

Dilution of the solution increases the degree of ionization. 

Substances which ionize increase the electrical conductivity 
of the solution, and the measure of the conductivity is a measure 
of the degree of ionization. 

* Qualitative Chemical Analysis. 



8 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

A given substance may ionize differently under different 
conditions, e.g., phosphoric acid may ionize as H + and (H 2 P0 4 )~ 
or as H+.H+ and (H.P0 4 )~ or as H+H+H+ and (P0 4 )~ The 
negative ion of sulphuric acid may be (HS0 4 )~ or (S0 4 )~. The 
various atoms of hydrogen of an acid do not ionize with equal 
facility and the terms primary, secondary, and tertiary ioni- 
zation may be applied to such cases as the above example of the 
ionization of phosphoric acid. 

The activity of a reagent depends upon the number of free 
ions in solution. 

Reaction between non-ionized molecules takes place very 
slowly. 

Water is the most important ionizing solvent. The alcohols 
cause less ionization, and the saturated hydrocarbon compounds 
as Benzene, Chloroform, or Gasolene, very little indeed. 

Water itself hydrolyzes to a slight extent and the utilization 
of the water ions in forming new molecules constitutes " Hy- 
drolysis." 

Complex ions may themselves be ionized in the presence of 
other ionizable compounds. 

Mass Action. — The quantity of the reagent has long been 
recognized as a factor in chemical reaction, e.g., nitric acid 
will replace hydrochloric acid in combination if the nitric acid 
is in sufficient excess, or if the hydrochloric acid is in excess 
the reverse reaction may take place. The completion of a 
reaction is often impossible without excess of one or the other of 
the substances involved. The precipitation of insoluble salts 
depends in many cases upon the quantity of reagent available 
which in turn may depend upon the degree of ionization. 

The application of these facts to the study of the deposition 
of tartar is one of our present problems. 

Chemical Equilibrium. — On page 5 we saw how a certain 
reagent might act in a given way or the reverse according to the 
temperature employed. If we couple this idea of chemical 



INTRODUCTION 9 

activity with the one given in the preceding paragraph we can 
easily picture conditions which will result in chemical equilib- 
rium (not inactivity). This has been defined as the point at 
which two opposite reactions acquire the same velocity.* 



Solution and Precipitation. 

"Solution is the equal distribution of a body in a liquid, 
the resulting mass being in all parts homogeneous and fluid 
enough to form drops," according to an old definition quoted 
in " Colloids and the Ultramicroscope " by Dr. Richard Zsig- 
mondy. 

We can readily adopt this definition for present use provided 
our conception of homogeneity is sufficiently elastic to include 
" Colloidal " solutions, and if we remember that the fluidity is 
not necessarily permanent as we have a number of recognized 
solid solutions among the alloys. See Chapter XII. 

The Law of Partition. — If two immiscible solvents of a 
given substance are brought together the amount of the sub- 
stance held in solution by each solvent will be in proportion to 
the solubility of the substance in each solvent respectively, e.g., 
Fe(CyS) 3 is more soluble in ether than in water, hence in a mix- 
ture of water and ether a proportionately larger amount of the 
salt would be dissolved by the ether. 

The solvate theory of solution of Professor H. C. Jones f 
is briefly, that soluble substances form a large number of defi- 
nite compounds with the solvent; that the number and com- 
plexity of these hydrates diminish as the concentration of the 
solution increases or as the temperature rises; and that, for the 
most part the union is between the solvent and the ions, rather 
than the molecules, of the dissolved substance. 

* Jones, " New Era in Chemistry," p. 28. 

f This theory is explained in detail in Professor Jones' book " A New Era 
in Chemistry," Chapter IX. 



IO SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

The colloids are distinguished from crystalloids by their 
inability to pass through parchment membrane. In colloidal 
solutions the substance (colloid) may be considered as in sus- 
pension or a state of subdivision so nearly complete as to ap- 
proach closely to the homogeneity of crystalloidal solution. 

In many colloidal solutions the particles are large enough to 
interfere with the passage of light and the preparation is more or 
less opaque. In some, however, this is not noticeable except 
by use of polarized light and special apparatus. 

There is no sharply defined line between the suspensions and 
the colloidal solutions, and it is often true that the homogeneity 
of a solution is dependent upon the " grossness of our means of 
observation." (Zsigmondy.) 

Colloidal substances as a class may be separated from the 
crystalloids by Dialysis, animal membrane suspended in dis- 
tilled water being used as a separating medium. The crystal- 
loids will pass through the membrane into the pure water, 
while the colloids remain behind. The use of the dialyzer as 
applied to saliva analysis is shown on page 316. 

Osmosis signifies the passage of water only through a mem- 
brane, tending to correct inequalities of pressure produced by 
differences in molecular concentrations of two solutions. 

This is usually illustrated by dropping potassium f errocyanide 
solution into copper sulphate. The drop of potassium ferro- 
cyanide becomes surrounded by a film of copper f errocyanide, 
through which water alone will pass. Membrane of this charac- 
ter is known as semipermeable. 

Porous cups are prepared for demonstrations of osmosis by 
precipitating within the pores of the cup or cell the ferrocyanide 
of copper. 

Osmotic pressure is the pressure produced within a semi- 
permeable cell by passage of water from the outside; or, as 
stated by Holland, it is " That push of the molecules of a solute 
upon its solvent which causes a flow through a membrane into 
the solution." 



INTRODUCTION II 

Precipitation signifies throwing out of a substance in solid 
form from solutions. The precipitation may be brought about 
in three ways: 

First, by change of temperature, when the substance pre- 
cipitated is the same as that previously held in solution; 

Second, by change in the character of the solvent, which 
likewise involves no chemical change and hence, like the first, 
may be regarded as a physical method. 

The third method depends upon the formation of a new sub- 
stance and is, of course, a chemical method. 

Illustrations, — First method: The separation of crystals of 
lead chloride by cooling a hot solution of the salt. 

Second method: Precipitation of barium chloride from saturated 
solution by strong hydrochloric acid. 

Third method: Any double decomposition resulting in the 
formation of an insoluble compound. 

Weights and Measures 

Measures. — The metric system of weights and measures 
and the Centigrade thermometer are largely used in all scientific 
work. The dentist, however, has also considerable use for 
troy weights and apothecaries' measures if he considers at all 
the composition of his gold solders, dental alloys, mouth washes, 
local anesthetics, etc. Hence, a few equivalents are here 
given. 

The meter is the primary unit of the metric system and was 
originally calculated as one ten-millionth part of the quadrant 
from the equator to the pole. 

i meter = ioo centimeters = iooo millimeters or 39.37 

inches. 
1 centimeter = 10/25 or 0.3937 of an inch. 
1 cubic centimeter = 16.23 minims or 0.0338 of a fluid ounce. 
1000 cubic centimeters (c.c.) = 1 liter or 2.1 13 pts. 



12 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

The weight of i c.c. of pure water at the temperature of its 
greatest density (4 C.) is taken as a unit of weight and called 
a gram (gramme). 

1 gram = 15.43 grains. 

1000 grams = 1 kilogram (kilo) = 35 oz. 120 grains or 2.2 

lbs. avoir. 
1 inch = 2.54 centimeters or 25.4 millimeters. 
1 oz. av. = 28.3495 grams or 437.5 grains. 
1 fluid oz. = 8 fluid drams, 29.57 cx -> or 456 grains of water. 
1 fluid dram = 3.7 c.c. 
1 troy oz. = 8 drams (3) or 480 grains. 
1 troy oz. = 24 scruples (3) or 20 pennyweight (pwt. or 

dwt). 
1 scruple = 20 grains, 1 pennyweight = 24 grains. 
1 grain = 64 milligrams. 
1 pint = 473.11 c.c. 

1 gallon = 8 pints, or 3785 c.c, or 231 cubic inches. 
1 lb. avoir. = 7000 grains or 453.59 grams. 

Measure of Temperature. — We shall constantly meet ref- 
erence to both the Centigrade and Fahrenheit scales and an 
understanding of the relationship of the two methods is essential. 

The thermometer is graduated by marking the point at which 
the mercury stands when the instrument is placed on melting 
ice; and again the point reached by the mercury when the 
thermometer is surrounded by dry steam under ordinary at- 
mospheric conditions. 

On the Centigrade thermometer, the lower or freezing point 
is marked zero, the upper or boiling point is marked one hundred, 
and the intervening space divided into one hundred equal de- 
grees. On the Fahrenheit scale, these points are marked respec- 
tively 32 and 212 and the scale is divided into 180 ; hence, 
i° C. equals i.8° or 9/5 Fahrenheit, and i° F. equals 5/9 of 
a Centigrade degree. Providing for the different freezing points 



INTRODUCTION 13 

(o° and 3 2 ), we can formulate a rule for converting tempera- 
ture records from one scale to the other, as follows: 

To convert Centigrade to Fahrenheit, take 9/5 of the given 
number of degrees and add 32. 

To convert Fahrenheit to Centigrade, subtract 32 from the 
given number and take 5/9 of the remainder; e.g., 



20°C. 


= 68°F. 


-s°c. 


= +2 3 °F. 


77° F. 


= 2S°C 


14° F. 


= -io°C. 



Absolute Temperature. 

According to the Law of Charles or of Gay-Lussac, gases 
(free molecules) contract 1/273 °f their volume, measured at 
o° C, for every Centigrade degree that the temperature falls; 
so it is assumed that, at a point 273 below the Centigrade zero, 
no further contraction would be possible, molecular motion 
would cease and all things become solid. This temperature has 
been called the absolute zero and temperature recorded from 
this point absolute temperature; thus, water freezes at 273 C. 
absolute temperature. 

Gravity. 

Specific gravity is the relative weight of equal bulks of 
different substances, one of which is taken as a standard. 

The standard is usually water for liquids and solids. 

The standard for gases may be air or hydrogen. 

When gases are referred to hydrogen as a standard, the term 
density is often used instead of specific gravity, and, to avoid con- 
fusion, this usage is recommended; i.e., the density of carbon 
dioxide is 22, while its specific gravity compared with air is 
about 1.53. 



14 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

The density of a gas will, according to the Law of Avogadro, 
be one-half its molecular weight. 

The specific gravity of a liquid may be diminished by the 
solution of a gas, as in case of solution of ammonia; or it may 
be increased, as in case of solution of hydrochloric acid. 

The boiling point of a liquid is raised by the solution of solids, 
and often by the solution of gases. 

Cryoscopy. 

The freezing point of liquids is lowered by the solution of 
other substances. As the amount of reduction of temperature 
necessary to change the liquid to the solid has been found to be 
in direct proportion to the amount of dissolved substance, it 
becomes possible to make many valuable determinations by 
this method. For accurate work, it is necessary to use a special 
thermometer graduated into hundredths of a degree. The use 
of the freezing point of a solution in determining the amount of 
the dissolved substance is known as cryoscopy, and is of great 
importance in both physical and physiological chemistry. 



CHAPTER II. 
THE METALS AND THEIR SALTS. 

Qualitative Analysis. 

The metals occur free in nature to quite an extent, but more 
often combined with other elements. These combinations are 
chiefly as oxides, sulphides, carbonates and silicates, and in one 
or more of these four forms the great mass of metals contained 
in the earth's crust may be found. 

Metallic sulphates are found to a considerable extent. 

Other natural sources of the metals are phosphates and chlo- 
rides, also smaller amounts of nitrates and comparatively slight 
amounts of bromides, iodides and fluorides. Metals are ex- 
tracted from their ores chiefly by reduction with some form of 
carbon. In case of the oxides this reduction takes place directly, 
according to this reaction: 2 CuO + C = 2 Cu + CO2. 

In case the metallic combination is a sulphide, the ore is first 
" roasted " in the air, whereby the sulphur is burned off and an 
oxide, which may then be reduced as above, is formed: 
2 CuS + 3 2 = 2 CuO + 2 S0 2 . 

The native carbonates are reduced to oxides by calcination, as 
CaC0 3 + heat = CaO + C0 2 . 

The silicates must first be changed to carbonates by fusion 
with alkali carbonates; then the reduction may be carried on as 
before: 

MgSi0 3 + NaaCOa = MgC0 3 + N^SiOs; 
MgC0 3 + heat = MgO + C0 2 . 

The metals, from certain physical properties, have been vari- 
ously classified. Thus, in the older books we read of the Noble 

is 



16 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

metals, those unaffected by heat, as gold, silver, and platinum; 
the Base metals, such as iron; the Bastard metals, those easily 
crystallizable, as antimony and zinc; the Metalloids, sodium and 
potassium. 

As the fact that the properties of metals were to a con- 
siderable extent dependent upon conditions of temperature and 
pressure became better understood, other classifications came to 
be used, and we may group them according to the chemical 
behavior of their salts, irrespective of their properties as metals. 
Thus Ag, Pb, and Hg (mercurous) form a group of metals 
whose chlorides are insoluble in water or dilute acids. These 
metals may consequently be thrown out of solution or precipi- 
tated by the addition of HC1 to any solution of their salts. We 
therefore let Ag, Hg', and Pb constitute the First Analytical 
Group, and HC1 is the First Group Reagent. 

In like manner we find a group of nine metals that are 
precipitated from dilute acid solution by hydrosulphuric acid 
(H 2 S). These metals are Cu, Cd, Bi, Hg, As, Sb, Sn, Au, and 
Pt, and constitute the Second Analytical Group, and H 2 S is the 
Second Group Reagent. 

The fact that the sulphides formed by the first four of these 
metals are insoluble in ammonium sulphide, and those formed 
by the last five are soluble, furnishes a simple method of separat- 
ing this group into two parts, a and b: 

Pb,* Cu, Cd, Bi, and Hg constituting Group II (a) and 

As, Sb, Sn, Au, and Pt, Group II (b). 

Thus, the metals are divided into various analytical groups, 
each with its own peculiar group reagent. Different groupings 
are possible, and hardly any two analysts will employ exactly 
the same scheme for identifying all the metals, although the 
following group divisions are generally used: 

* Lead is included in this group because it is not entirely separated as a 
chloride in Group I, traces of it remaining in solution even after addition of HC1. 



THE METALS AND THEIR SALTS 1 7 

Analytical Groups. 

Group I. — Ag, Pb, and Hg'. Metals that form insoluble 
chlorides and are precipitated from aqueous solution by 
HC1 (the group reagent). 

Group II (a). — Cu, Cd, Bi, Hg", and Pb. Metals that 
form sulphides insoluble in dilute HC1 solution and also 
insoluble in ammonium sulphide. 

Group II (b). — As, Sb, Sn, Au,"and Pt. Metals that form 
sulphides insoluble in dilute HC1 but soluble in yellow 
ammonium sulphide, or alkaline hydrates. 

Group III. — Fe, Al, and Cr. In solutions free from H 2 S 
and which do not contain phosphates, oxalates, tartrates, 
or salts of certain other organic acids these three metals 
may be separated by ammonium hydrate (NH 4 OH). 

Group IV. — Co, Ni, Mn, and Zn. Metals forming sulphides 
soluble in acid but insoluble in alkaline solution. Ammo- 
nium sulphide, (NH^S, is the group reagent. 

Group V. — Ba, Sr, Ca, and Mg.* Metals forming car- 
bonates, insoluble in alkaline solutions. The group re- 
agent is ammonium carbonate, (NH 4 ) 2 C0 3 . 

Group VI. — K, Na, Li, NH 4 . Metals which cannot be 
precipitated by any single reagent and for which it is 
necessary to make individual tests. 

It is our purpose to take up the study of the metals according 
to their analytical grouping: first, the deportment of their 
salts in solution; later, the metals themselves and their specific 
application to dentistry. 

* In the process of analysis, magnesium is held in solution by the presence of 
NH4CI and is not thrown out as a carbonate with the other three members of the 
group. 



CHAPTER III. 
METALS OF GROUP I. 

Silver, Ag (Argentum). 

The Metal. — Atomic weight 107.88. Silver occurs free in 
masses usually containing gold and copper; as sulphides, such 
as silver glance (Ag 2 S) and in combination with sulphides of 
antimony, lead, and copper. It also occurs as silver chloride, 
(AgCl) known as " Horn Silver " or Kerargyrite. 

Properties. — Silver fuses at 954 C, forming a revolving 
globule on charcoal or plaster without oxidation. 

At high temperatures, however, silver occludes or absorbs 
oxygen to the extent of twenty- two times its volume; but as the 
mass cools the absorbed gas is entirely given off, sometimes 
resulting in a roughened surface of the metal. 

This property may be overcome by alloying with copper or 
by covering with a considerable layer of common salt. 

Silver blackens in the presence of sulphur or hydrogen sul- 
phide. The so-called oxidized silver is a result of heating the 
metal with a solution of potassium sulphide. 

Silver dissolves in hot H 2 S0 4 with evolution of S0 2 . It is 
readily soluble in nitric acid with formation of AgNOg, colorless 
crystals, without water of crystallization. 

Silver amalgamates readily, and the " amalgamation process " 
is one of the important methods for its reduction from the ore. 

This process, briefly, is as follows: The ore is roasted with 
salt, producing chloride of silver; this, in suspension in water, is 
reduced by metallic iron, 

2 AgCl + Fe = FeCl 2 + 2 Ag. 
18 



METALS OF GROUP I 19 

The mixture treated with mercury forms an amalgam from 
which the mercury can be driven off by heat. 

Alloys. — Important alloys of silver are United States coin 
silver, consisting of silver 90 parts, copper 10 parts; and Sterling 
silver consisting of silver 92.5 parts, copper 7.5 parts. 

Amalgam alloys contain from 50 to 60% of silver, alloyed 
with tin and slight amounts of other metals such as copper, zinc, 
and gold. (See page 125.) 

A silver platinum alloy used for base plates, clasps, etc., con- 
tains from 12 to 35% platinum and is much harder than pure 
silver. 

Von Eckart's alloy,* a French preparation, used for a similar 
purpose, contains 3.53 parts silver, 2.40 parts platinum, and 
1 1. 7 1 parts copper. Silver solders are alloys of varying propor- 
tions of silver, copper, and zinc, the silver running from 60 to 

80%. 

Compounds. — Salts of silver are liable to decomposition by 
action of light with reduction in greater or less degree to metallic 
silver. The salts change from violet to black according to the 
amount of silver reduced. Such reduction is illustrated in the 
use of the ordinary photographic plates and paper. 

Silver oxide (Ag 2 0), a dark brown powder, may be produced 
in the wet way, i.e., by precipitation of soluble silver salts with 
hydroxides of the fixed alkalis. 

2 AgN0 3 + 2 NaOH = Ag 2 + H 2 + 2 NaN0 3 . 

Silver hydroxide (white) may be formed if the above reaction 
is brought about in alcoholic solution; but it is a very unstable 
compound, quickly changing to Ag 2 + H 2 0. Silver thiosul- 
phate, Ag 2 S 2 3 , may be precipitated white from solution of silver 
nitrate and sodium thiosulphate. Excess of the thiosulphate 
produces a soluble double salt NaAgS 2 3 . This fact may be 
utilized in the removal of silver stains. 

* Hepburn, page 60. 



20 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Fused silver nitrate in the form of pencils or small sticks is 
used as an escharotic, and is known as " Lunar Caustic." Dilute 
lunar caustic consists of equal parts of AgN0 3 and KN0 3 fused 
together in pencil form. 

Analytical Reactions. — Make the following tests with a 
weak solution of AgN0 3 (about 2%). Write the reactions and 
enter color and solubility of each precipitate formed in labora- 
tory note-book.* 

AgN0 3 with HC1 gives a white curdy precipitate of AgCl 
which darkens by action of sunlight. If Ag solution is very 
dilute, the precipitate will assume the curdy appearance and filter 
more easily if it is heated and rotated quite rapidly in the test- 
tube. Allow the precipitate to settle. Decant the liquid care- 
fully, divide precipitate into two parts, and test its solubility 
in dilute nitric acid, also in ammonia water. 

AgN0 3 with KBr gives a white precipitate of AgBr, less 
easily soluble in ammonia than the AgCl. 

AgN0 3 with KI gives a pale yellow precipitate of Agl, 
insoluble in ammonia. 

AgN0 3 with H 2 S gives a black precipitate of Ag 2 S. AgN0 3 
with K 2 Cr0 4 gives a red precipitate of Ag 2 Cr0 4 in neutral solu- 
tion. Test the solubility of Ag 2 Cr0 4 in NH 4 OH, HC1, and 
HN0 3 . 

Mercury, Hg (Hydrargyrum). 

The Metal. — Atomic weight 200.6. Occurs as red sulphide, 
cinnabar, and in small quantities amalgamated with silver or 
gold or combined with chlorine or iodine. It is the only metal 
which is liquid at ordinary temperatures, solidifying at — 39 C. 

The molecule of mercury consists of a single atom. 

* The author uses mimeograph copies of these experiments with space for the 
reactions and colors of precipitates, which are filled out without reference to the 
book and handed in by the student at the close of the laboratory exercise. 

These reactions have purposely been confined to such as may be applied to the 
process of analysis. 



METALS OF GROUP I 21 

Properties. — It boils at 360 C. and this wide range of tem- 
perature throughout which the fluid form is maintained, together 
with its comparatively great coefficient of expansion (about 
1/160), makes it particularly suitable for use in thermometers 
and other instruments for measuring temperature or pressure. 

At about 270 C. mercury combines with oxygen forming 
the red mercuric oxide. At the boiling point, it readily leaves 
other metals, with which it has combined, making the purification 
by dry distillation a comparatively simple process. The redis- 
tilled and chemically pure mercury is usually obtained by dis- 
tillation in vacuo. 

Certain mixtures of metals and mercury act as true chemical 
compounds forming an exception to the foregoing statement re- 
garding the separation of mercury by heat. (See Chapter XIII, 
page 119.) 

Alloys of mercury are amalgams and will be considered 
under this head. 

Compounds. — Mercury forms two series of salts; one, mer- 
curous, referable to the oxide Hg20, in which mercury exhibits 
a valence of one; and the other, mercuric, referable to HgO, 
the mercury having a valence of two. 

(Mercuric compounds will be considered under group two.) 

Mercurous chloride, or calomel, may be made by the reduc- 
tion of HgCl 2 by a reducing agent, as S0 2 . 2 HgCl 2 + 2 H 2 
+ S0 2 = 2 HgCl + H 2 S0 4 + 2HCI; but the process commercially 
employed is usually to sublime a mixture of mercuric sulphate, 
sodium chloride and mercury. 

HgS0 4 + 2 NaCl + Hg = 2 HgCl + Na 2 S0 4 . 

Mercurous iodide, Hgl, is a greenish colored unstable salt 
produced by double decomposition of HgN0 3 and KI. 

Mercurous nitrate is an easily soluble salt produced by action 
of cold nitric acid on excess of mercury, a solution of which may 
be used for the study of mercurous precipitates. 

Note. — The solution of mercurous nitrate, upon standing, will be found to 
contain more or less mercuric nitrate, unless care is taken to keep excess of mer- 
cury in the bottom of the bottle. 



22 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Analytical Reactions. — HgN0 3 with HC1 gives a white 
precipitate of HgCl (calomel) . After the precipitate has settled, 
decant the liquid, and test the solubility of the HgCl in ammonia 
water. Does it dissolve? How does its behavior differ from 
that of AgCl? 

Alkaline hydroxides form with mercurous salts the black 
oxide Hg 2 0, a preparation of which, made with lime-water and 
calomel, is known as " black wash." 

Lead, Pb (Plumbum). 

The Metal. — Atomic weight 207.1. Occurs as sulphide 
(Galena), PbS; in lesser quantities as native carbonate (Cerus- 
site) ; also as phosphate, chromate, and sulphate. 

Lead is reduced from the sulphide in a reverberatory furnace 
by a few simple reactions as follows: 3 PbS + 5 2 = 2 PbO + 
PbS04 + 2 SO2; then, by increasing the heat without access of 
air, the sulphur is driven off and the lead separates by two 
double decompositions, 

2 PbO + PbS = 3 Pb + S0 2 and PbS0 4 + PbS = 2 Pb + 2 S0 2 . 

Properties. — Melting-point from 325 to 33 5 C. Lead is 
one of the softest of the metals and can be easily cut with a 
good knife. It is a very poor conductor of electricity. 

Presence of small quantities of antimony or arsenic tend to 
harden the metal.* 

Lead is very easily separated from its compounds by reduction 
with carbon. 

Lead is soluble in nitric or acetic acid, forming Pb(N0 3 ) 2 or 
Pb(C 2 H 3 2 ) 2 . 

Lead is also dissolved to a very slight extent by pure water 
containing oxygen, or by water containing C0 2 , mineral salts, or 
organic matter. It tarnishes in the air, with formation of a 
suboxide, Pb 2 0. 

* Hepburn, page 137. 



METALS OF GROUP I 23 

Alloys. — Lead forms a large number of important alloys 
among which are solders and fusible metals as given in Chapter 
XIV, and type metal which is an alloy of lead and antimony. 

Compounds. — Besides the suboxide of lead above mentioned, 
three more compounds of lead and oxygen are of interest. 

Litharge, PbO, is the yellow oxide used in pharmacy as the 
base of " Diacylon plaster." 

The black oxide, Pb0 2 , is used as an oxidizing agent. Red 
lead (minium) , Pb 3 4 , is practically a mixture of Pb0 2 and 2 PbO, 
and used as a source of Pb0 2 by treatment with HN0 3 . 
Pb 3 4 + 4 HNO3 = Pb0 2 + 2 Pb(N0 3 ) 2 + 2 H 2 0. 

Lead carbonate, as prepared by precipitation of soluble lead 
salts by alkali carbonates, has the composition (PbC03) 2 Pb(OH) 2 . 

The basic carbonate, prepared by exposure of the metal to 
fumes of acetic acid, C0 2 , and moisture, is known as " white 
lead," and is used in manufacture of paint. 

Lead acetate, or sugar of lead, formed by solution of the 
metal or the oxide, PbO, in acetic acid, is a white soluble salt 
crystallizing with three molecules of H 2 0. The solution has an 
acid reaction to litmus paper. 

Lead subacetate, or basic acetate of lead, a solution of which 
is known as Goulard's extract,* is made by boiling lead acetate 
solution with litharge. It is used in medicine as an external ap- 
plication and in physiological chemistry as a reagent. It deteri- 
orates by absorption of C0 2 and precipitation of a carbonate. 

Lead chromate (chrome yellow) is a yellow insoluble salt used 
as a pigment. 

Lead nitrate, an easily soluble white crystalline salt, may be 
used in the study of the analytical reactions of lead. 

Lead arsenate, a poisonous salt, is quite largely used for 
spraying trees. 

Analytical Reactions. — Pb(N0 3 ) 2 with 2 HC1 gives white pre- 
cipitate of PbCl 2 . Test its solubility in hot water and in NH 4 OH. 

* Preparation on page 428. 



24 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Pb(N0s)2 with NH4OH gives white precipitate of Pb(OH) 2 
insoluble in hot water. 

Pb(N0 8 ) 2 with H 2 S gives black PbS. Test solubility of 
precipitate in warm dilute HNO3. 

Pb(N0 3 ) 2 with H 2 S0 4 gives white precipitate of PbS0 4 , form- 
ing slowly in dilute solutions. 

Pb(N0 3 ) 2 with K 2 Cr0 4 (or K 2 Cr 2 7 ) gives a yellow pre- 
cipitate of PbCr0 4 . 

Pb(N0 3 ) 2 gives with KI a yellow precipitate, Pbl 2 . Avoid 
excess of the potassium iodide. 

By application of the reactions of the salts of Ag, Pb, and 
Hg', we may formulate a scheme for the separation and identi- 
fication of the metals of Group I as follows: 

Analysis of Group I. 

(Ag, Pb, Hg'.) 

To the clear solution to be tested add slowly dilute HC1 as 
long as any precipitation occurs. Filter and wash the precipi- 
tate once with cold water, add this washing to filtrate to be 
tested for remaining groups, then wash precipitate on the paper 
with several small portions of hot water.. 




AgCl and HgCl remain undissolved. 



PbCl2 is in the hot-water solution. 



^ 



Divide this hot-water solution into three parts and make 
three of the following tests for lead: First, with K 2 Cr 2 07, which 
gives yellow precipitate of PbCr0 4 . Second, with dilute H 2 S0 4 , 
giving a white precipitate of PbS0 4 . Third, with H 2 S water, 
giving black precipitate of PbS. Fourth, with KI solution, which 
forms a yellow precipitate of Pbl 2 . Write these reactions. 



METALS OF GROUP I 



25 



To undissolved residues of Hg and Ag chlorides add warm 
NH4OH. 



Hg remains on the paper, black, as Hg + NH 2 HgCl. 

Ag is dissolved by the NH 4 OH and may be precipitated 
as AgCl by adding HN0 3 to acid reaction. Presence of 
Hg in the black residue may be confirmed as in Group II 
(page 48). 




OUTLINE SCHEME FOR ANALYSIS OF GROUP I. 

To about one-third of a test-tubeful of the unknown solution add a few drops 
of HC1. 

Ppt. = AgCl, HgCl, PbCl 2 . Filter, add hot H 2 0. 



Residue = AgCl, HgCl. 
Add NH 4 OH. 



Residue = HgCl. 
Test, as above. 



Solution = AgCl. 
Test with HN0 3 . 



Solution = PbCl 2 . 
Test as on page 24. 



QUESTIONS ON GROUP I. 

Why wash the precipitated chlorides only once with cold 
water? 

Why is it necessary to wash the lead chloride out with hot 
water before using ammonia? 

Why is ammonia used? 

How does nitric acid reprecipitate silver chloride? 

Why is it necessary to use two or more confirmatory tests 
for the presence of lead? 

What other metal in group one would give a black precipi- 
tate with hydrogen sulphide water? 

What precaution must be used in testing for soluble salts of 
lead with potassium iodide? 



CHAPTER IV. 
METALS OF GROUP H. 

Copper, Cu (Cuprum). 

The Metal. — Atomic weight 63.57. Occurs free in vicinity 
of Lake Superior; also in western United States, Chili, and Spain, 
as sulphides, copper pyrites, chalcopyrite, CuFeS 2 ; and copper 
glance, chalcocite, Cu 2 S. Malachite green and malachite blue 
are native basic carbonates of copper. 

Properties. — Melting point 1084 C. Copper dissolves 
easily in nitric acid and with difficulty in hydrochloric acid; 
heated with sulphuric acid it forms copper sulphate, with the 
evolution of sulphur dioxide. Copper is second to silver as a 
conductor of heat and electricity. It expands slightly on solidi- 
fying and is corroded by carbon dioxide and moisture forming a 
green carbonate. 

Alloys. — The alloy with mercury, amalgam, was formerly 
used in dentistry to a considerable extent (page 122). Copper 
alloys in all proportions with gold, silver, nickel, and zinc. It 
hardens silver and gold, and is used in the manufacture of coins, 
jewelry and the solders used in crown and bridge work. Copper 
is also used in the preparation of bronze, brass, bell metal, den- 
tal gold, German silver, Mannheim gold, Mosaic gold, Dutch 
metal, and Aich's metal. For composition of copper alloys, see 
page 114. 

Compounds. — Salts and solutions of copper are usually blue 
or green. Copper forms two series of salts: the cuprous, of 
which there are but few important examples, and the cupric. 
Cuprous oxide, Cu 2 0, which is red in color (sometimes yellow 

26 



METALS OF GROUP II 27 

through admixture of cuprous hydroxide) is obtained by reduc- 
tion of cupric salts by organic substances such as sugar. Cu- 
prous chloride is used as a reagent for the detection of acetylene 
gas. Cuprous iodide is a white, insoluble powder used in the 
preparation of the white copper cements. (See page 138.) 

Cupric oxide, CuO, is a black powder formed by ignition of 
copper in the air or by boiling copper solution with the fixed 
alkali hydroxides. 

Copper arsenate and aceto-arsenite, the latter known as 
Paris- green, are both green powders which have been used as 
pigments and as insecticides. 

Copper sulphate, CuS0 4 , crystallizes with five molecules of 
water and is known as bluestone or blue vitriol. It is used ex- 
tensively in the " Gravity battery," and in copper plating. 

Verdigris is a sub-acetate or oxy-acetate of copper; composi- 
tion, CU20(C 2 H 3 02)2. 

Copper salts combine with ammonia, forming a series of 
" cupr ammonium " compounds freely soluble and of intense 
blue color. 

The chloride nitrate and sulphate are the common soluble 
salts. A 1% solution of either of these will give the analytical 
reactions. 

Analytical Reactions. — CuS0 4 withH 2 S gives CuS, a brownish- 
black sulphide. Test its solubility in (NH 4 ) 2 S and in warm 
dilute NHO3. 

CuS0 4 with NH4OH (one or two drops of reagent) will pre- 
cipitate Cu(OH) 2 , bluish white. Add more NH 4 OH to the same 
test-tube and note the result. To this clear solution add a 
sufficient amount of dry KCN to completely decolorize the liquid. 
Then add to the mixture some H 2 S water. Is the black CuS 
thrown out? The behavior of Cu solutions thus treated is due 
to the formation of double salts, the solution in ammonia being 
due to a compound of CuS0 4 and NH3, and the decolorization 
of the blue solution to one of Cu(CN) 2 and KCN. 



28 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

C11SO4 with K 4 FeCy 6 (potassium ferrocyanide) gives in acetic 
acid solution a red-brown precipitate of Cu 2 FeCy 6 . 

Metallic zinc or iron will precipitate copper from solution. 
Hold a knife-blade in a solution of CuS0 4 for a few seconds. 

Mercury in Mercuric Combination. 

Compounds of Dyad Mercury. — Mercuric oxide, HgO, is 
a red powder obtained by ignition of mercury in the air. Mer- 
curic oxide may also be prepared by precipitation of mercuric 
chloride with alkaline hydroxides. The oxide thus formed is 
yellow in color, and, when prepared by mixing mercuric chloride 
and lime water, forms the " yellow wash " used to a considerable 
extent in pharmacy. 

Mercuric chloride, HgCl 2 . This intensely poisonous salt is 
known by the fairly descriptive name of corrosive sublimate. 
It corrodes metals, such as zinc and iron; it coagulates albumin 
and acts as a corrosive poison when taken internally. 

It is made in a manner analogous to that used for the prepa- 
ration of calomel, i.e., by sublimation, the salts used in this 
instance being mercuric sulphate and sodium chloride alone. 
HgS0 4 + 2 NaCl = HgCl 2 + NaaS0 4 . 

Mercuric chloride is antiseptic and a disinfectant in dilu- 
tions of one to a thousand. Antiseptic tablets designed to give 
about this strength of solution by the addition of one tablet to 
one pint of water are made to contain 7.7 grains HgCl 2 and 7.3 
grains NH 4 C1, with sufficient purple coloring to advertise the 
nature of the tablets and thus act as a safeguard against acci- 
dental poisoning. Mercuric chloride is soluble in water and in 
alcohol. It is used in the preparation of antiseptic gauze, sterile 
cotton, etc., but, on account of its corrosive properties, cannot 
be used to sterilize instruments. 

Ammoniated mercury, mercur-ammonium chloride or white 
precipitate (NH 2 HgCl) is a white powder obtained by slowly 
pouring a solution of HgCl 2 into ammonia water. 



METALS OF GROUP II 20 

Mercuric iodide, red iodide (Hgl 2 ), is made by reaction of 
mercuric chloride with potassium iodide : 

HgCl 2 + 2 KI - 2 KC1 + Hgl 2 . 

Mercuric iodide is soluble in excess of either reagent, also in 
alcohol. 

Mercuric iodide combines with potassium iodide (KI) form- 
ing an iodo-hydrargyrate, used as a reagent in physiological 
chemistry (page 406), also as an alkaloidal precipitant. 

An alkaline solution of potassium iodo-hydrargyrate con- 
stitutes Nessler's reagent, used in analysis of water and of saliva 
as a test for ammonium compounds. 

Analytical Reactions. — A 2% solution of corrosive sub- 
limate (HgCl 2 ) may be used in demonstrating the reactions of 
dyad mercury. 

HgCl 2 with H 2 S gives first a white precipitate, turning yellow, 
brown, and finally black, as proportion of H 2 S increases. The 
black precipitate only is mercuric sulphide, and care must be 
taken to add H 2 S till this compound is produced. 

Test the solubility of HgS in (NH 4 ) 2 S and HN0 3 . 

To HgCl 2 solution add SnCl 2 . The mercuric chloride is 
reduced to mercurous chloride (HgCl, white) or metallic mercury 
(Hg, gray), according to proportions used: 

2 HgCl 2 + SnCl 2 = 2 HgCl + SnCl 4 , 

or HgCl 2 + SnCl 2 = Hg + SnCU. 

HgCl 2 with KI gives red Hgl 2 , easily soluble in excess of 
either of the reagents. 

HgCl 2 with NH4OH gives white precipitate of (NH 2 Hg)Cl, 
known as "white precipitate" (see ammoniated mercury). 
" Red precipitate " is a term sometimes used to designate the 
red oxide of mercury, HgO, made in the dry way. 



30 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Bismuth, Bi. 

The Metal. — Atomic weight 208. Bismuth does not occur 
in large quantities, but is usually found in the free state. Small 
amounts are obtained from the oxide, Bi 2 3 , bismuth ochre, and 
from the sulphide, Bi 2 S3- 

It is easily identified by means of the blowpipe test on plaster 
with S and KI (page 128). 

Properties. — Melting-point 2 68° C. It is a crystalline 
metal, expands upon cooling and readily unites with oxygen 
burning with a bluish name to bismuth oxide. At ordinary 
temperatures it is brittle and readily dissolved by nitric acid. 

Alloys. — The most important alloys from a dental stand- 
point are the fusible metals, Melotte's metal, Wood's metal, 
Rose's metal, Newton's alloy, etc. (page 128). 

Fletcher states that an amalgam with one part bismuth, 
fifteen parts tin, and fifteen parts silver, filed and amalgamated 
with four parts of mercury to one part of the alloy, will adhere 
to a flat dry surface and may be used as a metallic cement upon 
apparatus, giving an air-tight joint of great strength. 

Compounds. — Salts of bismuth as a rule require excess of 
acid for permanent solution; and, by adding a considerable vol- 
ume of water they are easily thrown out of solution as insoluble 
basic or oxysalts, the reaction of the nitrate being as follows: 

Bi(N0 3 ) 3 + H 2 = BiON0 3 + 2 HN0 3 . 

This may be demonstrated by allowing a few drops of bis- 
muth solution to fall into a comparatively large amount of water 
(two to six ounces) . A white cloud of insoluble oxysalt may be 
observed settling through clear water. This may be employed 
as a final test for bismuth in the course of systematic analysis. 

The subnitrate and the subcarbonate of bismuth are both used 
in medicine. The latter is a common starting-point in the 
preparation of other bismuth salts. 



METALS OF GROUP II 31 

Analytical Reactions. — The most available salt is the ni- 
trate, insoluble in water unless strongly acidulated. 

Use a 2% solution of Bi(N0 3 )3 in the following tests: 

Bi(N0 3 ) 3 with NH4OH gives white precipitate of bismuth 
hydroxide Bi(OH) 3 . 

Bi(N0 3 ) 3 with H 2 S precipitates Bi 2 S 3 , brownish black, in- 
soluble in (NH 4 ) 2 S, but soluble in warm dilute HN0 3 . 

Bi(OH) 3 reacts with sodium stannite (prepared by adding 
NaOH to SnCl 2 till precipitate dissolves) giving a black precipi- 
tate of metallic bismuth. 

4 NaOH + SnCl 2 = Na 2 Sn0 2 + 2 NaCl + 2 H 2 0. 
2 Bi (OH) 8 + 3 Na 2 Sn0 2 = 2 Bi + 3 Na 2 Sn0 3 + 3 H 2 0. 

Cadmium, Cd. 

The Metal. — Atomic weight n 2.4. Occurs associated with 
zinc in zinc blende. It is more easily volatile than zinc, and 
advantage is taken of this fact in effecting its separation from 
that metal. 

Properties. — Melting-point 33 2 C. Cadmium is a com- 
paratively soft metal though harder than zinc or tin. It is usu- 
ally found in trade in the form of rods which crackle somewhat 
like tin when bent. 

It dissolves slowly in sulphuric acid or hydrochloric acid with 
the evolution of hydrogen, and easily in nitric acid with the pro- 
duction of nitrogen oxides. It is also soluble in solution of 
ammonium nitrate, forming cadmium nitrite and ammonium 
nitrite. 

Alloys. — Cadmium is used as a constituent of fusible metals 
and rarely, in small proportion, in dental alloys. Its use in 
the latter case is objectionable on account of the production of 
yellow stain of cadmium sulphide which penetrates the dentine 
(page 123). 



32 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Analytical Reactions. — A 2% solution of the sulphate or 
nitrate may be used in studying the deportment of cadmium 
salts. 

CdS0 4 with H 2 S gives a bright yellow sulphide, CdS, soluble 
in dilute nitric acid. 

CdS0 4 with (NEL^S also precipitates the yellow sulphide. 

Cadmium sulphide forms slowly, and, in presence of Cu or 
other second-group metals, may escape precipitation if the re- 
agent is added in insufficient quantity. 

Arsenic, As. 

The Element. — Atomic weight 75.0. Arsenic is on the 
borderline between the metallic and non-metallic elements, its 
acid-forming properties predominating. It occurs associated 
with copper and iron sulphides, as arsenical pyrites, FeAs.FeS 2 ; 
as native sulphides, orpiment, AS2S3, and realgar, AS2S2; also 
to some extent as the trioxide, AS2O3. 

Compounds. — Arsenic forms two series of salts, the ar- 
senious, As m , and arsenic, As v , and it also acts as an acid radical 
forming arsenious and arsenic acids. In the process of analysis, 
arsenic compounds whether acid or basic are reduced to arseni- 
ous by action of hydrogen sulphide. It is most easily obtained 
in the form of the trioxide, As 2 3 , also known as arsenious acid 
or white arsenic. 

White arsenic is intensely poisonous; but, nevertheless, it 
has been very freely used in curing the skin of fur-bearing animals 
and otherwise as a preservative. In dentistry white arsenic is 
used to devitalize pulp. 

Arsenic is widely distributed in nature. It occurs in soft 
coal from which source it finds its way into the roadside dust 
and any substance capable of holding dust, such as the majority 
of fabrics, wall papers, etc. Arsenic is a common impurity in 
mercury, zinc, and commercial acids. Inasmuch as these things 
are largely used in the preparation of amalgam and cement 



METALS OF GROUP II 33 

fillings, it is necessary that considerable pains be taken to pre- 
vent the presence of the poison in sufficient quantity to cause 
irritation. 

The poisonous character of arsenic differs greatly with the 
combination in which it occurs. A gaseous hydride of arsenic, 
AsH 3 , being among the most poisonous of its compounds, while 
some of the organic compounds are claimed to be non-poisonous. 

Arsenic forms an insoluble arsenate with ferric hydrate; 
hence, freshly precipitated ferric hydroxide is the official anti- 
dote for arsenical poisoning. This is prepared by mixing 150 c.c. 
of dilute ferric sulphate solution (containing 50 c.c. of the U.S.P. 
" Solution") with a well-shaken mixture of 10 grains of oxide 
of magnesium in about 750 c.c. of water: 

Fe 2 (S0 4 ) 3 + 3 Mg(OH) 2 = Fe*(OH) 6 + 3 MgS0 4 . 

Fowler's solution containing 1% AS2O3 dissolved by use of 
potassium bicarbonate; a solution of arsenious acid containing 
1% AS2O3 dissolved by aid of two parts of HC1; Donovan's 
solution containing 1% each of Asl 3 and Hgl 2 ; and Pearson's 
solution containing 1% sodium arsenate are Pharmacopceial 
preparations of arsenic. 

Analytical Reactions. — A solution for studying the reactions 
of arsenic (As 111 ) is conveniently made by dissolving about 15 
grams of white arsenic in dilute NaOH solution by aid of heat, 
then diluting to one liter and acidifying slightly with HC1. 

To an arsenious solution, which may be represented by AsCU, 
add H 2 S water. A lemon-yellow precipitate of As 2 S 3 will be 
thrown down. Test the solubility of this precipitate in yellow 
ammonium sulphide and in ammonium carbonate. 

To the alkaline solution of the sulphide add excess of HC1; 
As 2 S 3 is precipitated. 

To an arsenious solution add (NH 4 ) 2 S in repeated small 
portions. 

In neutral solution, as of sodium arsenite, Na 3 As0 3 , silver 



34 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

pitrate will throw down yellow silver arsenite, soluble in excess of 
nitric acid or ammonia. 

SPECIAL TESTS FOR ARSENIC. 

Relnsch's Test for arsenic, applicable to any solution 
whether organic or not, and very valuable for a preliminary test, 
is made as follows: place the solution or mixture to be tested in 
a porcelain dish, acidify strongly with hydrochloric acid, add a 
small strip of bright copper foil (cleaned in dilute nitric acid and 
thoroughly washed in distilled water) and boil for ten or twenty 
minutes, adding sufficient water to replace loss by evaporation. 
Remove the copper foil; a dark gray to black coating is an indi- 
cation of arsenic but not conclusive, as some other substances, 
mercury and antimony in particular, give similar deposits. 

To prove the presence of arsenic, roll the foil as tightly as 
possible and place it in the bulb of a small glass matrass (Fig. i). 



Fig. i. 

Heat the bulb over a very small luminous flame, when tetra- 
hedral or octahedral crystals of arsenious trioxide (AS2O3) will de- 
posit in the constricted portion of the tube. These may be iden- 
tified by microscopical examination. There will be sufficient air 
in the matrass for the formation of the oxide and the test becomes 
much more delicate than if heated in the ordinary open tube as 
often recommended. 

Gutzeit's Test is made by placing the suspected solution 
in a test-tube, acidifying with sulphuric acid, adding a few small 
pieces of arsenic-free zinc, and, as hydrogen begins to be given off, 
placing over the mouth of the tube a piece of filter-paper carry- 
ing a drop of a strong solution of silver nitrate. The presence 
of arsenic is indicated by the darkening of the moistened filter- 
paper in accordance with the following reactions: 



METALS OF GROUP II 



35 



The nascent hydrogen, liberated by action of the zinc upon 
the acid, forms with any arsenic present the gaseous arsenious 
hydride which, in contact with the filter-paper wet with silver 
nitrate solution, produces a brown or black stain of metallic 
silver, while the arsenic becomes arsenious acid, H3ASO3. The 
stain may possibly be yellow by formation of a compound of 
silver arsenide and silver nitrate, but, as a rule, moisture is 
present in sufficient amount to insure the decomposition of this 
compound. 

Antimony will give a similar brown or black stain (not 
yellow) , but the presence of arsenic may be conclusively demon- 
strated by making Fleitmann's Test, which is conducted in 
the same way as the preceding, except that the hydrogen is 
evolved in alkaline solution, either by means of zinc and strong 
potassium hydroxide solution (Zn + 2 KOH = K 2 Zn0 2 + H 2 ) 
or by sodium amalgam (made with arsenic-free mercury) and 
water (NaHg* + H 2 = NaOH + Hg + H). In this case the 
antimony hydride is not formed ; so a stain thus obtained con- 
stitutes a positive test for arsenic. 

Marsh's Test for arsenic (or antimony) 
consists of a simple hydrogen generator with 
glass tip for burning the gas, as shown in Fig. 2. 
In this apparatus antimony and arsenic are 
converted into the gaseous hydrides, arsenic 
hydride, and antimony hydride ; and if a piece 
of cold porcelain is pressed down upon the 
flame, arsenic or antimony will be deposited 
as metallic stains (mirrors) upon the porcelain. 

Traces of antimony may be retained in the 
generator by the introduction of a piece of 
platinum-foil, the antimony being precipitated 
upon the platinum to which it adheres quite strongly. 

To distinguish between arsenic and antimony spots the follow- 
ing tests will suffice: 




Fig. 2. 



36 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 



Arsenic. 
Brown-black, lustrous spots. 
Soluble in solution of hypochlorite of 

lime or soda. 
Easily volatilized. 



Antimony. 
Dead brown or black surfaces. 
Insoluble in solution of hypochlorite of 

lime or soda. 
Volatilized at red heat. 



The Marsh-Berzelius Test for arsenic is the most delicate 
of all and the one to which we resort in detecting arsenic in the 
saliva or the urine. By this method one two-hundredth of a 
milligram or about 1/12800 of a grain can be easily shown as a 
brown deposit in the constricted tube at about the point K, Fig. 3. 




The apparatus used in this test is shown in Fig. 3, and consists 
of a small Erlenmeyer flask, or wide-mouth bottle, fitted as a 
hydrogen generator, A, and connected with a drying- tube, B, 
rilled with fused calcium chloride, then with a tube of hard glass, 
C, drawn out to a very small diameter for half its length. 

The generator A is charged with arsenic-free zinc, and dilute 
sulphuric acid (1/5) introduced through the thistle-tube E. 
After all air has been driven from the apparatus, light the escaping 
hydrogen at T, then the Bunsen burner D, and allow the gen- 



METALS OF GROUP II 



37 



erator to run for about twenty minutes, thus making a blank 
test of apparatus and reagents; if at the end of this time the 
hard glass is perfectly free from any deposit the suspected liquid, 
which must have been freed from organic matter (process de- 
scribed in detail in chapter on Urine Analysis), may be introduced 
in portions of about 10 c.c. each. 

The flame should be spread somewhat so as to heat at least 
one inch of the glass tube. This may be ac- 
complished, in the absence of a burner-tip, 
by placing an inverted V-shaped piece of as- 
bestos board, one inch wide, over the heated 
part of the tube. 

The presence of arsenic increases the evo- 
lution of hydrogen and, unless the solution 
is added gradually, the arsenious hydride 
may be driven so rapidly past the flame as 
to escape decomposition, or the tube may 
become heated to such an extent that arsenic 
will not be deposited. 

The escape of arsenic at T may be 
noticed by the bluish color of the flame 
and by the characteristic garlic odor. 

Antimony is similarly deposited as a 
dead-black stain instead of brown-black, 
and as antimony is less easily volatile 
than arsenic the deposit will be nearer 
the flame, possibly on both sides of it. 

Mercuric Bromide Test. — Sanger and 
Black* have modified the Gutzeit test 
making the determination of arsenic a quantitative one as 
follows: The arsenious hydride is passed through a drying tube 
containing filter-paper (in bulb, Fig. 4) wet with lead acetate 

* Proceedings of the American Academy of Arts and Sciences, Vol. XLIII, 
No. 8. October 1907. 




Fig. 4. 



38 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

solution to absorb sulphur compounds. Then the gas is passed 
through absorbent cotton in upper part of drying tube, and then 
over a paper moistened with mercuric chloride (small tube above 
drying tube) when the arsenic produces a yellow to brown color 
on the strip of filter-paper. 

The delicacy of this test may be increased by using mercuric 
bromide in place of mercuric chloride. The process has the 
advantage of being independent of heat and consequent danger 
of exploding any mixture of hydrogen and air. The HgBr 2 paper 
is stained yellow to brown beginning at the end next to the 
generator, and by carefully regulating conditions the extent of 
the stain may have a quantitative value. 

Arsenic compounds (As v ), as NasHAsO^ are of 'but little 
interest from the dentist's standpoint. 

All arsenic compounds are reduced by nascent hydrogen to 
arsenious combinations, then to elementary arsenic, then to 
arsine, (AsH 3 ), hence the special tests given for arsenious com- 
pounds are applicable. 

Free chlorine, nitric acid, and potassium ferricyanide oxidize 
arsenious compounds to arsenic, and in this condition the ar- 
senic is not easily volatilized and organic matter may be destroyed 
by deflagration (in presence of excess of nitrates) with but slight 
loss of arsenic. 

Antimony, Sb (Stibium). 

The Metal. — Atomic weight 120.2. Occurs native in Aus- 
tralia, and as the sulphide SD2S3, known as stibnite or antimo- 
nite from which it may be easily reduced by heating with 
metallic iron according to the following reaction: 

Sb 2 S 3 + 3 Fe = Sb 2 + 3 FeS. 

Properties. — Brittle crystalline substance volatile at high 
heat. It ultimately burns to antimonious oxide (Sb 2 3 ). Sol- 
uble with difficulty in sulphuric or hydrochloric acids. 




METALS OF GROUP II 39 

With nitric acid, antimony acts in a similar manner to tin, 
forming an oxide which may be antimonious (Sb 2 3 ) or anti- 
monic (St^Os) according to quantity and concentration of acid 
used (Prescott & Johnson). 

Alloys. — Antimony is used in making type metal, Britannia 
metal, and rarely in low-grade dental alloys. 

Compounds. — The salts of antimony may be classified as 
antimony salts, referable to the hydroxide Sb(OH) 3 , and anti- 
monyl salts, referable to SbO(OH). 

Butter of antimony, antimony trichloride, SbCl3, when pure, 
is a colorless solid of buttery consistency, hence its name. It 
may be formed by direct union of constituent elements. 

Salts of antimony tend to form oxycompounds and are held 
in solution by excess of acid. The antimonious chloride SbC^, 
in solution with hydrochloric acid is precipitated by excess of 
water as a white oxychloride SD4CI2O5, also known as " powder 
of Algaroth. ' ' The antimonic chloride in like manner precipitates 
the antimonic oxychloride, SbOCls- Demonstrate by turning 
1 or 2 c.c. of SbC^ solution into a large excess of water. 

Tartar emetic, K(SbO)C 4 H40 6 , may be prepared by boiling 
antimony oxide and bitartrate of potassium, filtering and allow- 
ing the hot solution to crystallize. It crystallizes with one-half 
molecule of water. 

Analytical Reactions. — A 2% aqueous solution of tartar 
emetic may be used in the following tests: 

To an antimony solution represented by SbCl 3 add H 2 S 
water: Sb 2 S 3 is precipitated orange-red. Test solubility of the 
precipitate in (NH^S and in (NHO2CO3. 

How does it differ from arsenic? 

Upon the addition of HC1 in excess to the ammonium sul- 
phide solution the Sb is reprecipitated, but not necessarily, as 
SboS 3 , but more usually as Sl^Ss or a mixture of the two sulphides. 



40 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Tin, Sn (Stannum). 

The Metal. — Atomic weight 119. Cassiterite, or tin-stone, 
nearly pure stannic oxide (Sn0 2 ), is by far the most important 
source. The free metal has been found associated with gold. 

Banca tin from the East Indies and block tin from England 
are pure varieties of the commercial article. 

Properties. — Pure tin will give a peculiar crackling sound 
when bent, due to the crystalline structure of the metal. Tin 
is very malleable at the ordinary temperature, being fifth 
in the list of malleable metals (see page 111), but becomes 
brittle when heated to about 200 C. 

Hydrochloric acid dissolves tin slowly, forming stannous 
or stannic chlorides according to the proportion and temperature 
of the acid used. 

Cold dilute nitric acid will dissolve tin, forming stannous 
nitrate. 

Metallic tin is not dissolved by strong nitric acid, but is 
converted into a white, insoluble metastannic acid. Hot dilute 
nitric acid will produce this same result. This acid, upon 
standing, changes to normal stannic acid which is easily soluble 
in acids; hence, in making use of this reaction in the analysis ot 
amalgam alloys, it is not well to allow the nitric acid solution 
ol the alloy to stand too long before filtering. 

Alloys. — Pewter usually contains Sn, Pb, Cu, and Sb, some- 
times Zn. Rees's alloy Sn 20 parts, gold 1 part, and silver 2 
parts. Tin is also a constituent of solders, fusible metals, Bab- 
bitt's metal, bell metal, and bronze. 

An alloy of tin and mercury (tin amalgam) is used for " silver- 
ing mirrors." 

Compounds. — The salts of tin are not used in medicine but 
are useful as laboratory reagents. 

The chloride (SnCl 2 ) prepared as suggested under properties 
ot the metal is used in solution as a test for mercury. 



METALS OF GROUP II 41 

The stannic salts are the more stable and this solution of 
stannous chloride easily becomes stannic chloride unless excess 
of metallic tin is kept in the solution. 

Stannous nitrate may be produced by the action of cold 
nitric acid as follows: 

4 Sn + 10HNO3 = 4 Sn(N0 3 ) 2 + 3 H 2 + NH4NO3. 

Tin may act as an acid-forming element in such compounds 
as sodium stannite (Na 2 Sn0 2 ) produced by the solution of stan- 
nous hydrate in sodium hydrate, 

Sn(OH) 2 + 2 NaOH = NaaSnCfe + 2 H 2 0, 

or sodium stannate produced when stannic oxide is fused with 
sodium hydrate, 

Sn0 2 + 2 NaOH = Na 2 Sn0 3 + H 2 0. 

Metallic zinc thrown into a tin solution will precipitate the 
tin as follows: SnCl 2 + Zn = ZnCl 2 + Sn. 

This reaction is used in the separation of tin from antimony 
in the second group; and, in order to obtain the tin in soluble form 
suitable for a final test, it is necessary to add hydrochloric acid 
sufficient first to dissolve all the zinc present; otherwise it (tin) 
may remain adhering to the zinc. 

Tin, like arsenic and antimony, forms two series of salts, the 
stannous (Sn 11 ) and the stannic (Sn IV ). A little HC1 treated 
with excess of granulated tin till hydrogen is no longer given off 
furnishes a solution of stannous chloride suitable for the follow- 
ing experiments : 

Analytical Reactions. — SnCl 2 with H 2 S gives brown pre- 
cipitate of SnS, soluble in (NBLi) 2 S, insoluble in (NH 4 ) 2 C0 3 . 

SnCl 2 with HgCl 2 gives a white or gray precipitate, as ex- 
plained on page 29 under " Mercury," and is used as a test for 
presence of mercury. It may also be used as an alkaloidal pre- 
cipitant. 

Strong solutions of SnCl 2 in presence of metallic Sn keep 



42 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

fairly well, but dilute solutions without an excess of tin oxidize 
very rapidly to stannic combinations and cease to be of value 
as reagents. 

Gold, Au (Aurum). 

The Metal. — Atomic weight 197.2. It is usually found 
uncombined, but mixed with various impurities. It occurs 
frequently as native alloys; of these, two might be mentioned: 
Calverite, AuTe2, contains 40% gold, and Sylvanite, or graphic 
tellurium, (AuAg)Te 2 , contains 24-26% gold. 

Gold is extracted from its ores in various ways, the simplest of 
which is that known as placer mining. This consists of a process 
of washing out the particles of gold which separate themselves 
easily because of their heavier weight compared to that of the 
gravel and stones among which they are found. Hydraulic 
mining, the utilization of a great force of water to break up the 
auriferous rock, has come to the aid of placer mining in getting 
the largest masses ready for the washing process. Other methods 
are quartz mining in which mercury is used to attract the gold, 
and the chlorination process. 

Properties. — Melting-point 1064 C. Pure gold is a soft 
metal of yellow color, unless in a very fine state of subdivision 
produced by the precipitation of the metal when the color varies 
from purple to brown or nearly black. Gold is more malleable 
and more ductile than either silver or copper. Gold is second 
to silver as a conductor of electricity. 

Gold is insoluble in simple acids, but may be dissolved in 
nitrohydrochloric acid (aqua regia) with formation of auric 
chloride. Gold also unites easily with bromine or iodine, form- 
ing AuBr 3 or AUI3. 

Gold possesses the property of adhesiveness in a peculiar 
and very marked degree. By virtue of this the metal can be 
welded without heat; continued hammering tends to lessen or 
weaken this property. 



METALS OF GROUP II 



43 



When gold-foil is heated to redness (annealed) it recovers the 
cohesive property which has been largely lost by hammering. 
The toughness and ductibility are also increased. It is recom- 
mended that the heating be done in an electric furnace or on 
plates of mica or platinum, thus insuring uniformity of effect 
throughout the mass which it is practically impossible to ob- 
tain by holding the metal in the flame. See Dental Cosmos, 
Vol. XL VII, page 233. 

Non-cohesive gold, or gold in which the cohesive property 
cannot be developed by heating, may be prepared by alloying 
or treatment with carbon. Corrugated gold is of this variety 
and is prepared, according to Essig, by 
carbonization of unsized paper in inti- 
mate contact with the metal. See Essig, 
Dental Metallurgy, page 173, or Hodgen 
and Millbury, page 209. 

Alloys. — Gold is alloyed with copper 
to make it harder and more durable for 
use in the manufacture of jewelry, plate, 
and coin. It is alloyed with silver for 
the purpose of reducing its melting- 
point. Copper and zinc, or copper, 
silver, and zinc may be used in this 
way (See page 132 for formulae for gold 
alloys.) 

The term " carat " * as applied to gold signifies 1/24 part and 
is used as a measure of purity of an alloy, 22 carat gold being 
22/24 pure gold. Twenty carat gold is 20/24 pure, etc. The 
amount of gold in a given alloy may be determined approxi- 
mately by use of a device shown in Fig. 5, much used by 
jewelers, consisting of a series of standard alloys and a piece of 
stone upon which the test is made. The tips are standard 

* The term carat is also used by jewelers as a unit of weight. The legal stand- 
ard for U. S., since July 1, 1913, has been 200 milligrams. 




Fig. 5. 



44 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

alloys. Parallel markings are made on the stone with the alloy 
in question and with the tip supposed to correspond to it; then 
the addition of a drop of strong nitric acid to the marks and a 
careful comparison of their appearance will show if the two are 
of the same composition. 

If the composition of an alloy is known, the value in carats 
may be determined by the following: 

Rule to determine the carat of a given alloy: Multiply 24 
by the weight of gold used and divide result by total weight of 
alloy. For instance, if an alloy is made containing 9 parts of 
gold and 3 of another metal, the total weight will be 12 and 
the calculations 24 X 9 -r 12 = 18. The alloy is an 18-carat 
gold. 

Gold may be raised to a higher carat by the following rule: 
Multiply weight of alloy used by difference between its carat 
and that of the metal to be added. Then divide product by the 
difference between the carat of the metal added and that of the 
required alloy. The figure thus obtained represents the total 
weight of required alloy. Subtract from this the weight of ma- 
terial taken and the difference is weight of pure or alloyed gold 
to be added. (From Hall's Dental Chemistry.) 

To reduce gold to a required carat Essig takes the following 
rule from Richardson's Mechanical Dentistry: " Multiply the 
weight of gold used by 24 and divide the product by the required 
carat. The quotient is the weight of the mass when reduced, 
from which subtract the weight of the gold used, and the remain- 
der is the weight of the alloy to be added." 

Analytical Reactions. — A one-half per cent, solution of AUCI3 
may be used in the following tests: 

H 2 S with AUCI3 gives dark brown Au 2 S 3 (auric sulphide), 
soluble in yellow ammonium sulphide. 

Gold is reduced to the metallic state by many of the other 
metals, as Pb, Cu, Ag, Sn, Al, Sb, Fe, Mg, Zn, and Hg; also 
by ferrous sulphate, stannous chloride, and oxalic acid. 



METALS OF GROUP II 45 

Add a freshly prepared solution of ferrous sulphate to a little 
acid solution of AuC^. Gold is precipitated as follows: 
AuCla + 3 FeS0 4 = Au + Fe^SO^s + FeClg. 

Stannous chloride precipitates from gold solution the " purple 
of Cassius," consisting of a mixture of gold and oxide of tin in 
colloidal forms. 

Gold is only slowly precipitated by oxalic acid; 2 AuCU + 
3 H2C2O4 = 6 HC1 + 6 C0 2 + 2 Au, but, as Pt is not precipitated 
at all by this reagent, it is possible to separate Au and Pt in 
solution of the chlorides, by this means. 

KI will give a dark-green precipitate of Aul 2 provided the 
KI is in excess; if the gold is in excess, the precipitate is apt to be 
the yellow Aul (aurous iodide) . In the presence of a considerable 
excess of KI the Aul 3 is kept in solution as the potassioauric 
iodide, KIAuI 3 . The reduction of this double salt by sodium 
thiosulphate is made the basis of the method to determine the 
quantity of Au in a given alloy, as described in the chapter on 
Volumetric Analysis. 

Platinum, Pt. 

The Metal. — Atomic weight 195.2. Platinum, like gold, 
is found principally in the free or metallic state, often associated 
with the rarer metals such as iridium, rhodium, osmium, and 
palladium; also combined with gold, silver, and copper; a native 
arsenide, PtAs2 is found in the mineral sperrylite. 

Properties. — Melting-point nearly 2000 C. Platinum solu- 
bilities are similar to gold; aqua regia forms the chloride PtCl 4 , 
or the chloroplatinic acid H 2 PtCl 6 . Platinum is a white metal 
unaffected by oxygen, or the fluids of the mouth, hence adapted 
for use in permanent dental appliances. When melted it ab- 
sorbs oxygen in a manner similar to silver and when finely 
divided (platinum black) will absorb or occlude gases to a re- 
markable degree, one part of platinum black under favorable 



46 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

conditions absorbing in this way over eight hundred times its 
volume of oxygen. As this occlusion necessarily means conden- 
sation of the gas advantage may be taken of this property to 
bring about chemical union of gases which will not unite at ordi- 
nary temperatures, such as hydrogen and oxygen, oxygen and 
sulphur dioxide. Platinum black may be made by strong ignition 
of platinum chloride. 

Alloys. — Platinum alloys quite easily with other metals, 
particularly lead; and platinum utensils may be destroyed by 
heating in contact with the compounds of metals easily reduced. 
Sulphur and phosphorus also attack platinum. 

Platinum 90% and iridium 10% give an alloy harder, more 
brittle, and more resistant to chemical action than pure platinum. 

Note. — Iridium is a rare metal of particular interest in connection with the 
platinum alloy given above. Its symbol is Ir; atomic weight is 193. 1; melting- 
point is about 2500 C. It occurs with platinum; also associated with osmium 
with which it forms a very hard alloy insoluble in aqua regia. 

An alloy of platinum and osmium is practically insoluble in 
acids, is very hard and capable of great expansion. Of the vary- 
ing proportions of the two metals which may be used those of one 
to ten per cent, of osmium with ninety to ninety-nine per cent, of 
platinum prove the most successful. One part of osmium in 
such an alloy will take the place of two and one half times its 
weight of irridium.* 

" Platinum color," for coloring enamel, is made, according 
to Mitchell's Dental Chemistry, by precipitating platinum from 
a solution of PtCLt by boiling with KOH and grape sugar; then, 
grinding this finely divided platinum with feldspar in the pro- 
portion of one part platinum to sixteen parts feldspar. 

Analytical Reactions. — PtCLt + H 2 S gives a precipitate of 
sulphide of platinum almost black, soluble in yellow ammonium 
sulphide. 

Platinum solution with NH4CI precipitates yellow ammonium 
* Hepburn, page 112. 



METALS OF GROUP II 



47 



platinic chloride, (NH4) 2 PtCl 6 , crystalline. Potassium chloride 
also gives a yellow crystalline precipitate of K 2 PtCl6, isomorphous 
with the ammonium compound. (Plate III, Figs, i and 3.) 
These reactions may be made quantitative by using neutral, 
fairly concentrated solutions and adding an equal volume of 
alcohol. 

Both of these double salts are soluble in excess of alkali, 
and reprecipitated by HC1. 

Stannous chloride reduces PtCLt to PtCl 2 but forms no pre- 
cipitate. Metallic Zn will precipitate platinum as a fine black 
powder or spongy mass. 



Analysis of Group II. 

Separation of parts (a) and (6) 

A portion of the clear filtrate, from Group I, containing a 
slight excess of HC1 is tested for metals of Group II by the 
addition of H 2 S water.* 

If a precipitate is obtained, warm the whole of the solution 
and pass in H 2 S gas for from three to five minutes, which pre- 
cipitates all metals of the group as sulphides. Filter. 

Break point of filter-paper with glass rod and wash Group II 
into beaker with warm (NH 4 ) 2 S; digest hot for a few minutes. 

Filter and wash the precipitate till wash-water shows only 
traces of CI. Throw away all wash-water except the first. 



Group II (a). Cu, Cd, Bi, Hg, and Pb. 




Group II (b). As, Sb, Sn, Au, and Pt. 



* A preliminary test is made on a part of the solution because in the absence 
of Group II, the analysis of Group III can be made more easily without the pres- 
ence of H 2 S. 



48 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Analysis of Group II (a). 
Dissolve the precipitate off the paper with hot dilute HN0 3 . 




Hg, if present, will remain on paper, black. 



Filtrate contains nitrates of Pb, Cu, Cd, and Bi 



Test black residue on paper for Hg 11 by dissolving in aqua 
regia and precipitating with SnCl 2 . For reaction between SnCl 2 
and HgCI 2 , see page 29. Aqua regia may be made by mixing 
two or three parts of HC1 with one part of HN0 3 . Free CI is 
liberated which dissolves the HgS as HgCl 2 . 

3 HC1 + HNO3 = N0C1 + 2 H 2 + Cl 2 . 

If lead is present in Group I, the filtrate above will contain 
traces which must be separated by adding a few drops of H 2 S0 4 
and allowing to stand at least fifteen minutes. Filter. 



PbS0 4 remains on paper. 



Filtrate contains Cu, Cd, Bi. 




To the filtrate add NH4OH till alkaline; Bi separates as Bi 
(OH) 3 , white. Filter. Confirmatory test for bismuth may be 
made by pouring over the precipitated Bi(OH) 3 on the paper a 
solution of sodium stannite. If bismuth is present the precipitate 
turns black in accordance with the reaction given on page 31. 



METALS OF GROUP II 



49 




Bi(OH) 3 . 



Cu and Cd. 



Divide the filtrate (Cu and Cd) into two parts. A blue color 
indicates presence of Cu. With one part test for Cu by making 
it acid with acetic acid and adding KiFeCye, which will give 
a brown precipitate of Cu 2 FeCy 6 . With the other part test for 
Cd by adding solid KCN very carefully till all blue color has 
disappeared; then a little H 2 S water will give a yellow preci- 
pitate of CdS if cadmium is present. 

Analysis of Group II (b). 

To the ammonium sulphide solution add HC1 till acid. A 
very fine white precipitate may be sulphur only. 

Filter and wash. Throw away wash-water. Pierce paper 
and wash sulphides into large test-tube or small beaker. Add 
10 c.c. of (NH4) 2 C0 3 and heat for a few minutes. Filter. 



Sb, Sn, Au, Pt sulphides are on the pape^. 




Arsenic sulphide is in the filtrate. 



Add HC1 and Zn and make Gutzeit's test (page 34) and if 
necessary Fleitmann's (page 36) or Marsh's (page 35). 

Dry this precipitate upon paper and place paper and pre- 
cipitate in a porcelain evaporator, add concentrated HC1 and 
heat. (This must be done under the hood.) Dilute and filter, 
when Au and Pt will remain undissolved. 



50 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 




Au and Pt. 



Sb and Sn. 



To the Sb and Sn solution add a little Zn and a piece of 
platinum-foil. The antimony and tin will both be reduced to 
the metallic state, the Sb being deposited on the Pt as a brown 
or black coating. Presence of Sb may be confirmed by remov- 
ing the Pt, washing carefully, treating with (NFL^S, and dry- 
ing, when the coating will become Sb 2 S 3 , orange-red. 

To the solution to be tested for Sn add HO enough to dis- 
solve all the Zn which has been added, filter, and test filtrate 
with HgCl 2 (page 29). 

Dissolve the insoluble residue of Au and Pt (the residue 
will be dark-colored if either of these metals are present) in 
aqua regia and divide solution into two parts. 

Test one part for gold with solution of FeS0 4 , or a mixture 
of SnCl 2 and SnCU (page 45). 

Test the other part for Pt by adding NH4CI, allow to stand 
over night adding a little alcohol, and a precipitate of ammo- 
nium platinic chloride will be obtained, yellow and crystalline 
(see Plate III, Fig. 1, page 171). 



METALS OF GROUP II 



51 



OUTLINE SCHEME FOR ANALYSIS OF GROUP II. 

To the warmed filtrate from Group I add H2S. A ppt. may be sulphides of 
As, Sb, Sn, Au, Pt, Cu, Cd, Bi, Hg, and Pb. 
Filter and treat with warm (NHO2S. 



Residue is Group II (a), page 47, and consists 

of sulphides oj Cu, Cd, Bi, Hg. and Pb. 
Treat on paper c warm dil. HNO3. 



Residue 

is Hg. 

Dissolve 

in aqua 

regia and 

test c 

SnCl 2 

(page 29) . 



Solution Cu, Cd, Bi, and Pb. 
Add H2SO4 and filter. 



Ppt. 

is 

PbSO, 



Solution is Cu, Cd, and 
Bi. AddNH*OHand 
filter. 



Ppt. is 
Bi(OH) 5 



Solution is Cu and 
Cd. 



Test for 
Cue HA 

and 
KUFeCye. 

(page 49-) 



Test for 
Cd5KCN 
and H 2 S. 



Solution= As, Sb, Sn, Au, and Pt. Reprecipitate 
c HC1, filter and treat ppt. c strong (NH^COa 



Residue=Sb, Sn^Au, and Pt, sul- 
phides. Treat c cone. HC1, dilute 
and filter. 



Residue. 
Au and Pt. Dissolve 
in aqua regia and di- 
vide. 



Part I. 

Test for 

Au c FeS0 4 

(page 45). 



Part II. 

Test for 
Ptc 

NH4CI 
and alco- 
hol. 



Solution. 

Sb and Sn. 
Test for 
SbcPt 

foil and Zn. 



Test for 
Sn in fil- 
trate c 
HgCl 2 
(page 50). 



Solution. 

As. Make 
Gutzeit's 
or Fleit- 
mann's 

test for As 
(pages 34 
and 36) . 



QUESTIONS ON GROUP II. 

Why is it necessary to wash the precipitate of Group II 
practically free from CI before dissolving in warm HN0 3 ? 

How does the Hg found in Group II differ from the Hg in 
Group I ? 

Does the Pb found in Group II differ from the Pb in 
Group I ? 

Before making the final test for Sn, why is it necessary to 
dissolve all the Zn which has been added ? 

In precipitating Group II why should the solution be made 
acid with HC1 before adding H 2 S ? 

Why is it better to use H 2 S gas rather than H 2 S water in 
precipitating metals of Group II ? 

Before testing for Cd why add KCN to decolorize the copper 
solution ? 



52 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Why is a confirmatory test for bismuth desirable ? 

Why must organic matter be destroyed before making Marsh's 
test for arsenic ? 

What reagent would you select for the precipitation of gold 
and give reason for choice ? 

Why is sulphuric acid preferable to hydrochloric in making 
Marsh's test for arsenic ? 



CHAPTER V. 
METALS OF GROUP m. 

Iron, Fe (Ferrum). 

The Metal. — Atomic weight 55.84. Iron occurs widely 
distributed in nature combined with oxygen as Magnetite or 
magnetic iron ore, Fe 3 4 ; as Red Hematite, Fe^; or Brown 
Hematite or Limonite, 2 Fe203.3 H2O; with sulphur as Iron 
Pyrites or Fool's Gold, FeS2; and with carbon as Spathic iron 
ore or Siderite, FeC0 3 . 

The reduction of iron from its ores is typical of one of the four 
general methods, that is, reduction by carbon. This is carried 
out in the blast or smelting furnaces, which are so constructed 
that a supply of coal, iron ore, and suitable flux may be intro- 
duced at the top of the furnace. The fusible slag consisting of 
the flux which has dissolved the impurities of the ore and the 
purified molten metal is drawn off from the bottom, thus admit- 
ting a continuous process. This melted iron, cast in molds as 
it comes from the furnace, constitutes our cast or pig iron, is 
brittle, and contains a considerable proportion of carbon, some- 
times as much as two and three- tenths per cent., and other im- 
purities. 

Wrought iron is produced by working melted iron in specially 
constructed furnaces so that the greater part of the impurities 
are removed. It contains less than six-tenths of a per cent, of 
carbon. 

Steel may be made by a more perfect removal of impurities 
in the Bessemer converter and subsequent mixture of exact pro- 
portions of carbon, phosphorus, and manganese. Steel contains 
from six- tenths to one and six- tenths per cent, of carbon. 

53 



54 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Reduced iron or " iron by hydrogen " is prepared by the 
reduction of the heated oxide or hydroxide in a stream of hydro- 
gen gas, and consists of a very fine powder of pure metallic iron. 

Properties. — Melting-point 1275 C. Iron dissolves in 
hydrochloric or sulphuric acid with the evolution of hydrogen. 
In nitric acid, cold and dilute, ferrous and ammonium nitrates 
are produced. Warm dilute nitric acid forms ferric nitrate and 
nitric oxide. Iron is most magnetic of all metals; next in this 
particular come nickel and cobalt. 

Compounds. — Iron forms two classes of salts, ferrous, 
represented by ferrous sulphate, FeS0 4 ; and ferric, represented 
by ferric sulphate, Fe 2 (SO^s, or ferric chloride, FeCl 3 . 

Ferric sulphate, also known as Monsel's salt, is used as a 
styptic. 

Ferric chloride, FeCl 3 or Fe 2 Cl 6 , is made by dissolving iron 
in hydrochloric acid, oxidizing the ferrous chloride with nitric 
acid, and then driving off the nitric acid by evaporation. The 
resulting solution, however, contains traces of free nitric and 
considerable free hydrochloric acid. In the tincture of chloride 
of iron these acids react with the alcohol forming various ethers, 
to which the peculiarities of the tincture may be due. 

Copperas and green vitriol are commercial names for crys- 
tallized ferrous sulphate, FeS0 4 .7 H 2 0, which is used as a disin- 
fectant and, to a slight extent, in medicine as an astringent. 

Ferrous carbonate, (FeC0 3 )#(Fe(OH) 2 )y, prepared by double 
decomposition between ferrous sulphate and potassium or so- 
dium carbonate, is a medicinal preparation quite largely used 
as "Blaud's pills." 

Analytical Reactions. — A solution for demonstrating the 
reactions of ferrous salts is best made by saturating cold dilute 
sulphuric acid with clean iron wire. A three to five per cent, solu- 
tion of fresh crystals of ferrous ammonium sulphate may be used. 
The ordinary ferrous sulphate or " copperas " is almost sure to 
contain some ferric salt. Use a two to three per cent, solution of 



METALS OF GROUP III 55 

ferric chloride and make the following tests, comparing the de- 
portment of the ferrous and ferric solutions with each reagent. 
Write the reactions. 

H 2 S with pure ferrous salts gives no reaction; with ferric 
salts the iron is reduced to the ferrous combination, but gives no 
precipitate except sulphur. 

(NH 4 ) 2 S gives with ferrous iron a black precipitate of FeS; 
with ferric salts it gives a precipitate containing FeS and S. 

NH4OH precipitates Fe 11 as ferrous hydroxide, Fe(OH) 2 ; 
white if perfectly pure, but usually a dirty green from admixture 
of ferric compounds. The presence of NH 4 C1 prevents a complete 
precipitation as Fe(OH) 2 . 

With ferric salts, NH4OH completely precipitates the iron 
as brick-red ferric hydroxide, Fe(OH) 3 . 

K4FeCy 6 gives with ferrous salts a bluish-white precipitate 
of potassium ferrous ferrocyanide, K 2 FeFeCy 6 . 

With a solution of ferric salts the deep Prussian blue, ferric 
ferrocyanide, Fe 4 (FeCy 6 )3, is thrown out. 

With potassium ferricyanide, ferrous salts give a dark-blue 
precipitate of ferrous ferricyanide, Fe 3 (FeCy 6 ) 2 . With ferric 
salts no precipitation occurs, but the color may change to green 
or brown. 

KCyS or NE^CyS gives no reaction with pure ferrous salts, 
but with ferric salts a deep red solution of ferric thiocyanate, 
Fe(CyS) 3 , is produced. This red color is destroyed by addition 
of HgCl 2 , not affected by HC1, and may be extracted from the 
aqueous solution by shaking with ether in which the Fe(CyS) 3 is 
soluble. 

Aluminium, Al. 

The Metal. — Atomic weight 27.1. Aluminium as a con- 
stituent of clay, feldspar, mica, etc., constitutes a considerable 
part of the earth's crust. The principal sources are Cryolite, 
Bauxite, and Corundum. 



56 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Properties. — Melting-point 657 C. Aluminium is a silver 
white metal, a good conductor of heat and electricity, and one 
of the lightest metals, its specific gravity being 2.58. Aluminium 
is reduced in an electric furnace by the aid of charcoal and copper 
with which it amalgamates (Cowle's process). 

Alloys. — Aluminium alloys are not difficult to produce. 
The pure metal is used in making plates. A high proportion of 
aluminium in alloys is not desirable as it renders the alloy ex- 
tremely brittle. Alloys containing from five to thirty per cent, 
are of increasing importance. Aluminium bronze consisting of 
copper with five to twelve per cent, of aluminium is used as a 
base for artificial dentures. An alloy used in the preparation of 
analytical balances and scientific apparatus known as Magnalium 
contains aluminium and magnesium. 

Compounds. — The most important soluble salts of alu- 
minium are ammonia alum, NH4A1(S0 4 )2 12 H 2 0, potash alum, 
KA1(S0 4 )2 12 H 2 0, and aluminium sulphate, A1 2 (S0 4 ) 3 . 

The term alum is applied to any salt of definite crystalline 
form containing one molecule of a univalent sulphate, such as 
K2SO4 or Na 2 S0 4 , combined with one molecule of a trivalent 
sulphate, A1 2 (S0 4 )3, Fe 2 (S0 4 ) 3 or Cr 2 (S0 4 ) 3 , and crystallized with 
twenty-four molecules of water. The formula of alum, as given 
above, comprises just one-half of this combination. Alum need 
not contain any aluminium whatever so long as it conforms to the 
foregoing requirements, e.g., chrome alum may be NHiC^SO^ 
12 H 2 and ferric alum is usually NH4Fe(S0 4 ) 2 12 H 2 0. 

Analytical Reactions. — Use a 5% solution of either of these 
for the following tests: 

A1 2 (S0 4 ) 3 with (NH^S and H 2 gives a white precipitate of 
A1(0H) 3 . Write the reaction. 

Al(OH) 3 is likewise produced by NH4OH, Na 2 C0 3 , or NaOH; 
the precipitate is soluble in excess of fixed alkali hydroxides with 
formation of aluminates: 

Al(OH) 3 + KOH = KA10 2 + 2 H 2 0. 



METALS OF GROUP III 57 

The alkaline peroxides produce aluminates from Al(OH) 3 . 
Demonstrate by covering a little precipitated aluminium hy- 
droxide in a porcelain dish with a very little water; then sprinkle 
on to the mixture sodium peroxide in small portions till a clear 
solution results. Nitric or hydrochloric acid will decompose the 
aluminate forming again the aluminium salt, which can be 
reprecipitated by ammonia as Al(OH) 3 . 

The alkaline aluminates may also be formed by fusion with 
Na 2 C0 3 and KNO3 and then may be dissolved in hot water. 

From the solution of KA10 2 the Al may be precipitated as 
Al(OH) 3 by excess of NH4CI (difference from Zn, page 66). 

The presence of organic acids, tartaric, oxalic, etc., inter- 
feres with the precipitation of aluminium hydroxide and may 
entirely prevent it. The presence of ammonium chloride favors 
its precipitation. 

Chromium, Cr. 

The Metal. — Atomic weight 52. Occurs as chrome iron ore 
or chromite, FeOCr 2 3 . 

Properties. — Chromium is a hard, grayish colored metal, 
not used as such in dentistry. 

Compounds. — Chromium forms two oxides, one basic in 
character, Cr 2 3 , which forms the basis of chromic salts, as Cr 2 
(S0 4 ) 3 , Cr 2 Cle(CrCl 3 ),* etc.; the other, Cr0 3 , is an acid anhydride, 
crystallizes as dark-red needles, and gives rise to two series of 
salts: neutral chromates, such as K 2 Cr0 4 , and acid chromates 
or dichromates, K 2 Cr 2 7 . 

Analytical Reactions. — The soluble chromic salts most 
easily obtained are chrome alum, KCr(S0 4 ) 2 , chromic sulphate, 
Cr 2 (S0 4 ) 3 , and chromic chloride, CrC^. With a 5% solution of 
either of these the following may be demonstrated : 

Cr 2 (S0 4 ) 3 with (NH 4 ) 2 S gives greenish precipitate of Cr(OH) 3 . 

* There is a series of chromous salts, OQ2, Cr(OH) 2 , etc., corresponding to 
a chromous oxide, CrO, but the oxide itself is not known. 



58 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Similarly to aluminium, the chromium hydroxide is precipi- 
tated by the alkaline carbonates and the alkaline sulphides as 
well as by the hydroxides; and then by boiling the Cr(OH) 3 with 
NaOH or KOH, or by fusing with Na 2 C0 3 and KN0 3 , or by the 
action of sodium peroxide and heat, chromates of the alkalis 
may be produced. The chromate upon the addition of nitric 
acid becomes the dichromate. This solution after neutralization 
with ammonia will give a characteristic yellow precipitate of 
PbCr0 4 with soluble salts of lead. 

The solid dichromate K 2 Cr 2 7 with strong H 2 S0 4 gives, in 
the presence of chlorides, the reddish-brown gas Cr0 2 Cl 2 (chloro- 
chromic anhydride or chromium dioxychloride) used as a test for 
chlorides (page 96) . 

Analysis of Group III. 

(Fe, Al, Cr. Phosphates and oxalates being absent.) 

The filtrate from Group II must be freed from H 2 S by boil- 
ing with a few drops of HNO3 in a porcelain dish till a drop re- 
moved by a glass rod does not blacken filter-paper wet with a 
solution of lead acetate. This treatment also serves to oxidize 
the iron (reduced by H 2 S) to ferric salt and at the same time 
concentrates the solution. To the clear solution thus obtained 
add 10 c.c. of NH4CI solution, then NH4OH till alkaline, when 
the metals of this group will separate as hydroxides: Fe(OH)3 
brick-red, Al(OH) 3 white, Cr(OH) 3 bluish-green. Filter and 
wash. 



Group III. 

Groups IV, V, and VI. 





METALS OF GROUP III 59 

Transfer the precipitated hydroxides to a porcelain dish. 
Cover with a little water. Add in small portions sodium per- 
oxide not exceeding in total bulk the original precipitate. Add 
a little more water and boil- till oxygen ceases to be evolved, add- 
ing water if necessary to keep up the volume of the solution. 
Filter out iron if it is present. 



Fe(OH) 3 . 

Al and Cr as negative ions. 



Wash the precipitate remaining on the paper (Fe) and dis- 
solve in dilute HC1. Divide resulting solution (FeCU) into two 
parts and confirm presence of Fe by testing one with K4FeCy 6 
(blue precipitate) and the other with KCyS (red solution). 

If iron is found, determine in original substance whether 
ferrous or ferric, by use of tests described on page 55. 

To the nitrate containing sodium aluminate and chromate 
add HNO3 producing A1(N0 3 ) 3 and Cr 2 07 = . Add 5 c.c. of ten 
per cent. NH4CI solution and make alkaline with NH4OH, which 
precipitates Al(OH) 3 . Filter, acidify filtrate with acetic acid 
and test for presence of chromium with lead acetate solution. 
(Precipitate is PbCr0 4 .) 

The presence of aluminium may be confirmed as follows: 

Transfer the precipitate of aluminium hydroxide to a small 
evaporating dish, moisten with concentrated nitric acid, add a 
very tiny crystal of cobalt nitrate, and evaporate to dryness. 
Let the blue flame (O.F.) of the Bunsen burner play directly 
upon the residue in the dish. Aluminium produces the blue 
cobalt aluminate. 

The aluminium hydroxide should be as nearly white as pos- 
sible. If it is dark in color, dissolve it in nitric acid and repre- 



6o SALTS OF THE METALS AND QUALITATIVE ANALYSIS 



cipitate with ammonium hydroxide before treating with cobalt 
nitrate.* 

OUTLINE FOR ANALYSIS OF GROUP III. 

Take clear filtrate from Group II and boil with a few drops of HNO3 to expel 
H 2 S and oxidize Fe". Add NH4CI and NH4OH and filter. 



Ppt. A1(0H) 3 . Cr(OH) 3 . Fe(OH) 3 . Treat with Na 2 2 . Boil c H2O. 
Filter (page 58). 



Ppt. Fe(OH) 3 . Test 
5KCNSandK4Fe 
(CN)«(pageS9)- 



Sol. NaAlOo and Na 2 Cr04. Add HN0 3 =A1+++ and 
(Cr 2 7 )=." Add NH40H=A1(0H) 3 and Cr0 4 = 
Filter. 



Test for Al c Co(N0 3 ) 2 
(page 59)- 



Test for Cr04~ c 
Pb(C 2 H 3 2 ) 2 



Solution. 
Groups IV, V, 
and VI 



QUESTIONS ON GROUP III. 

Why boil off H 2 S before precipitating the group with NH4OH? 
WhyaddHN0 3 ? 

In making final test for chromium why is it necessary to 
acidify with acetic acid? 

What is the action of the peroxide of sodium in the separation 
of aluminium and chromium? 

Why is it necessary to test the original solution to determine 
the character of the iron? 

* For the detail of this test as well as for the general method of separation 
of this group by use of sodium peroxide, the author is indebted to Miss Mary E. 
Holmes, Associate professor of Chemistry at Mount Holyoke College. 



CHAPTER VI. 
METALS OF GROUP IV. 

Cobalt, Co. 

The Metal. — Atomic weight 58.97. Cobalt occurs in nature 
as an arsenide C0AS2, smaltite; also CoAsS, cobaltite. These 
ores are poisonous and have in times past caused the miners so 
much trouble that the name cobalt was applied to them, the 
word meaning, " A demon or mountain sprite." Metallic arsenic 
has also been called cobalt. These facts are probably responsible 
for an undeserved reputation which is sometimes attached to 
the pure oxide of cobalt. 

Analytical Reactions. — Use a 2% solution of nitrate. Crys- 
talline salts of cobalt are usually of pink color; anhydrous 
salts are blue. 

Co(N0 3 )2 with (NH^S gives precipitate of cobalt sulphide, 
black. Test solubility of this precipitate in HC1. 

Make a borax bead by fusing a little borax on the looped end of 
a clean platinum wire. When a bead of clear " borax glass " 
has been obtained, dip it in a little of the cobalt sulphide just 
formed, and fuse again. The color of the bead when cold is a 
deep blue. 

Note. — Be sure and make the fusion complete; the use of an insufficient 
amount of heat will account for much of the trouble experienced by students in 
obtaining satisfactory bead tests. 

Co(N0 3 ) 2 with KN0 2 forms a double nitrite, Co(N0 2 ) 2 
2 KN0 2 , soluble in water; but if sufficient acetic acid is added 
to produce a strong acid reaction, the solution heated, and then 
allowed to stand overnight, the cobalt is completely precipitated 
as another double salt, Co(N0 2 )2, 3 KN0 2 , yellow and crystalline. 

61 



62 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Nickel, Ni. 

The Metal. — Atomic weight 58.68. It occurs associated 
with Cobalt, sometimes with Iron or with Copper as a sulphide. 
Also it is found combined with magnesium as a double silicate 
called Garnierite, NiMg(Si0 3 ) 2 .3 H 2 0. Natural alloys of nickel 
with arsenic and with antimony are to be included among the 
sources of the metal. 

Properties. — The metal is white and hard, and has a high 
melting-point. It is soluble in dilute mineral acids, most easily 
in nitric. It is the least malleable of the common metals. It 
tarnishes very slowly in the air. 

Alloys. — The principal alloys are German silver, containing 
copper, nickel, and zinc, and an alloy of 25% nickel and 75% cop- 
per used by the United States Government in making five cent 
pieces. 

In contact with saliva German silver changes rapidly, and 
in consequence is usually gold plated when used for orthodontia 
appliances. 

Nickel plating. — Nickel is largely used for plating steel 
and copper. In this process metallic nickel is made the positive 
pole and substances to be plated are attached to the negative 
pole of a battery giving not more than five volts. The electro- 
lyte is a solution of nickel and ammonium sulphate made 
slightly alkaline with ammonia water. Nickel deposits on 
copper in a much more satisfactory manner than on iron, and 
from warm solution better than from cold. 

The following formulae are also recommended by Prinz : * 

Nickel sulphate 10 parts 

Sodium citrate 9 " 

Distilled water 280 " 

Nickel and ammonium sulphate 70 parts 

Boric acid 25 " 

Distilled water 1000 " 

In any case use pure nickel in sheet form as an anode. 

* Dental Formulary. 



METALS OF GROUP IV 63 

Analytical Reactions. — Use a 2% solution of the sulphate 
or nitrate. NiS0 4 with (NH 4 ) 2 S gives NiS, black. Test solu- 
bility in HC1. 

The borax-bead test applied to NiS or other nickel salt gives 
a bead yellowish brown when cold, but the color is easily masked 
by other metals. 

Ni salts with KN0 2 give the soluble double nitrite of sim- 
ilar composition to the Co salt, Ni(N0 2 )2, 2 KN0 2 . The nickel 
salt, unlike the cobalt, is not easily decomposed, and is not 
precipitated by heating with acetic acid. Advantage is taken 
of this fact in effecting the separation of cobalt from nickel 
(page 61). 

Manganese, Mn. 

The Metal. — Atomic weight 54.93. Occurs chiefly as the 
dioxide Mn0 2 , pyrolusite. 

Compounds. — The black oxide, manganese dioxide, is 
commercially important in the production of chlorine. By 
Weldon's process, the chlorine is obtained from hydrochloric 
acid, the pyrolusite acting as an oxidizing agent. 

The oxidation of manganese dioxide in the presence of potas- 
sium hydroxide results in the formation of potassium permanga- 
nate, KMn0 4 . This salt is a valuable disinfectant and is largely 
used. Its decomposition furnishes five atoms of available oxygen 
from every double molecule (K 2 Mn 2 8 ) . 

Condy's fluid, a commercial disinfectant, is a solution of 
potassium permanganate. 

Manganese salts are usually flesh-colored. 

Analytical Reactions. — A three per cent, solution of the sul- 
phate may be used in the following tests: 

MnS0 4 with (NH 4 ) 2 S gives flesh-colored precipitate of MnS. 
Test solubility in HC1. With a little of the precipitated MnS 
make a red-lead test for Mn as follows: 

Place in a test-tube a little red lead (Pb 3 4 ). Add three or 



64 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

four cubic centimeters of a solution of nitric acid (about one part 
of concentrated HN0 3 and one of H 2 0), and boil well. Add, 
by means of a glass rod, a little of the washed MnS to the mixture 
in the tube and boil again. Now dilute with water till the 
tube is about three-quarters full, and allow to stand till liquid is 
clear. If Mn is present, the supernatant fluid will be a pink to 
red color due to the formation of permanganic acid, HMn0 4 . 

Note. — HC1 or chlorides, even in small quantities, interfere with the reaction; 
hence it is recommended to make the test on the sulphide. Reducing agents must 
likewise be absent. When these precautions are observed the test is a very simple 
and an extremely delicate one. 

MnS0 4 with NaOH gives flesh-colored Mn(OH) 2 , insoluble 
in excess of reagent (separation from Zn) . 

Upon fusion with a mixture of KNO3 and Na 2 C03, man- 
ganese salts produce green manganates, as Na 2 Mn0 4 . 

Zinc, Zn. 

The Metal. — Atomic weight 65.37. Occurs chiefly as the 

carbonate, ZnC0 3 , calamine. A native carbonate of zinc is 

also known as smithsonite. The sulphide ZnS (zinc blende), 

and the silicate are also natural sources of the metal. 

Note. — The name calamine has also been given by Prof. Dana of Yale to a 
silicate of zinc, H 2 Zn 2 Si06. 

These ores of zinc, whether sulphide or carbonate, upon roast- 
ing in air are converted into oxide, and the oxide is easily reduced 
by carbon to metallic zinc. 

Properties. — Melting-point 420 C. (burns). The metal 
is bluish white in color, is brittle at ordinary temperatures, but 
malleable and ductile at 140 to 150 C. At 200 C, however, 
it again becomes brittle and fuses as above stated at 420 C. 
At 950 zinc boils and may be distilled; in air it ultimately 
burns to a white oxide. Whenever zinc ores are sufficiently 
rich in the metal the pure zinc may be separated by heating with 
carbon out of contact with the air to a temperature considerably 






METALS OF GROUP IV 65 

in excess of its boiling-point, when the zinc distills and may be 
condensed. 

Alloy. — Zinc is of considerable importance from a dental 
standpoint, the metal itself being used in the manufacture of 
counter-dies and solders; and, according to Mitchell's Dental 
Chemistry, it may be advantageously used in the proportion of 
one to one and five-tenths per cent, in silver-tin amalgam alloys. 
" It tends to control shrinkage, imparts a ' buttery ' plasticity 
to the amalgam, adds to the whiteness of the filling and assists 
in the maintaining of its color." See also page 124. 

Compounds. — The oxide of zinc combines with phosphoric 
acid and is peculiarly adapted to the preparation of dental 
cements. Zinc salts with alkaline carbonates precipitate a 
white basic carbonate, Zn 5 (0H) 6 (C0 3 ) 2 , which is used as a pig- 
ment in the preparation of paint and also as a source of pure 
oxide of zinc. 

The sulphate, ZnS0 4 , also known as white vitriol, is per- 
haps the most common salt. The chloride is a constituent 
of many commercial liquid disinfectants and antiseptics. The 
nitrate also is easily obtained. 

A two or three per cent, solution of any of these soluble salts 
may be used in the following tests: 

Analytical Reactions. — ZnS0 4 with (NH 4 ) 2 S gives a white 
precipitate of ZnS. 

Sulphide of zinc is the only white sulphide formed in the 
course of analysis of ordinary solutions, but the following white 
precipitates are formed: Sulphide of manganese is flesh-colored or 
dirty white. Aluminium hydroxide resembles sulphide of zinc 
in appearance and is precipitated by (NH^S. Yellow (NH^S 
added to an acid solution will precipitate sulphur, white, very 
fine and difficult to filter out. 

ZnS0 4 with NaOH (or KOH) gives a white gelatinous pre- 
cipitate of zinc hydrate, Zn(OH) 2 , soluble in excess of the reagent 
as Na 2 Zn0 2 (sodium zincate) . 



66 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Note. — Colorless gelatinous precipitates in slight amounts may escape de- 
tection, as it sometimes takes careful observation to see them, especially if the 
laboratory light happens to be poor. 

Na 2 Zn0 2 with H 2 S or (NH 4 ) 2 S gives precipitate of ZnS. 

From solution of Na 2 Zn0 2 the Zn may be precipitated as 
Zn(OH) 2 by addition of NH4CI, but further addition of the 
NH4CI redissolves the precipitate (distinction from Al, page 57). 

ZnS0 4 with K^FeCye gives white precipitate of zinc ferro- 
cyanide (Zn 2 FeCy 6 ), insoluble in NH 4 OH. 

Note. — The ferrocyanide and the sulphide are the only two zinc salts not 
soluble in NH 4 OH. (Prescott and Johnson, page 179.) 

Soluble zinc salts, with oxalic acid or oxalates, give a pre- 
cipitate of zinc oxalate sufficiently insoluble in alcohol and 
water to make it available for use in the quantitative separation 
of zinc from dental alloys. The crystals are of characteristic 
form, which may be recognized under a microscope (Plate II, 
Fig. 6, page 170). 

Analysis of Group IV. 

(Co, Ni, Mn, Zn.) 

(In the presence of phosphates, oxalates, borates, etc., 
examine this group by the scheme given on page 88.) 

To the clear filtrate from Group III add (NEL^S. A pre- 
cipitate may be NiS,* CoS, MnS, and ZnS. Wash the precipitate 
and treat with cold dilute HC1, which will dissolve MnS and ZnS 
only. 



CoS and NiS, black. 

MnCl2 and ZnGb in solution. 



* A black precipitate persistently passing through the paper is NiS, and some- 
times requires heating or concentrating before a clear filtrate can be obtained. 




METALS OF GROUP IV 



67 



Make a borax-bead test (page 61) of the precipitates on 
funnel in above figure. If a clear red-brown bead is obtained, 
Ni alone is present. If the bead is blue, Co is present, Ni may 
or may not be. 

Separation of Cobalt and Nickel. 

If Co is present, dissolve the black precipitate off the paper 
with aqua regia, evaporate in porcelain capsule practically to 
dryness, dissolve in H 2 0, add excess of acetic acid and potassium 
nitrite (KN0 2 ). Allow ,to stand over night, when Co will 
separate out as a yellow crystalline precipitate (page 61). 

Filter and test filtrate for Ni with NaOH, which gives a 
pale- green precipitate of Ni(OH) 2 insoluble in excess of the 
precipitant. 

Separation of Manganese and Zinc. 

Boil the HC1 solution of Zn and Mn to expel the H 2 S, then 
add a decided excess of KOH or NaOH and allow to stand ten 
minutes without heating. Mn will separate out as Mn(OH) 2 , 
while Zn will remain in solution as K 2 Zn0 2 . 



Mn(OH) a 



K2Z11O2. 



Test precipitate by the red-lead test for Mn, page 63. Test 
filtrate for Zn by adding H 2 S or a few drops of (NEL^S, which 
will precipitate ZnS, white. 





68 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

OUTLINE FOR ANALYSIS OF GROUP IV. 
To filtrate from Group III add (NH|) 2 S. Filter. 



QUESTIONS ON GROUP IV. 

Why dissolve the MnS and ZnS in cold and dilute HC1? 

Why is it necessary to separate all the Mn before testing 
for Zn? 

If traces of Co or Ni are dissolved by the HC1, how does it 
affect the final test for Zn? 

In this analysis (in absence of phosphates, etc.) what im- 
portant difference between the behavior of salts of Zn and Al? 

Why is it necessary to allow time for complete precipitation 
of Co with KN0 2 ? 

Why expel H 2 S before separating Mn? 

Where does this H 2 S come from? 






Ppt. = CoS, 


NiS, ZnS, MnS. Treat c dil. HC1. 


Residue. Co and Ni. Make borax 


Sol. Mn and Zn. Boil and heat c KOH or NaOH. 


bead test. Separate Co by means 
of KNO2 (page 61) 


Ppt. Mn(OH) 2 . Make red- 
lead test 


Sol. K 2 Zn0 2 . Add H 2 S = 
ppt. ZnS (page 67) 









CHAPTER VII. 
METALS OF GROUP V. 

The Alkaline Earths Ba, Sr, Ca, Mg. 

The common alkaline earth metals present similarity of 
properties which ally them more closely than the metals of some 
of the previous analytical groups. None of the metals occur 
free in nature. The metals themselves are isolated with con- 
siderable difficulty, with the exception of magnesium, and they 
all decompose water with evolution of hydrogen; calcium, stron- 
tium, and barium producing the decomposition at ordinary tem- 
peratures; magnesium, at high temperatures only. 

As a group they form insoluble carbonates, from which carbon 
dioxide is easily driven off by heat, leaving the oxide of the metal. 
This oxide unites with water, forming feebly soluble hydroxides. 
The solutions of the hydroxides are alkaline to litmus, and are 
used, to a considerable extent, in medicine, as antacids. 

There are two other metals belonging to this group. The 
-first, glucinum, also called beryllium, has an atomic weight of 
9.1. Soluble salts of glucinum are precipitated by ammonium 
hydroxide as white and gelatinous beryllium hydroxide. The 
precipitate somewhat resembles aluminium hydroxide. Ammo- 
nium carbonate also precipitates the hydroxide, which is easily 
soluble in excess of reagent. The solution, however, should 
not be boiled as prolonged boiling will cause the beryllium 
hydroxide to reprecipitate. 

Beryllium oxide unites with phosphoric acid, forming a 
phosphate similar in its properties to the basic phosphate of zinc, 
and its use is claimed by some manufacturers to be essential to 
the preparation of artificial enamels. (See page 138.) 

69 



70 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

The second rare metal belonging to this group is radium; 
atomic weight 226.4. The metal itself has not as yet been iso- 
lated. Its compounds are obtained from uraninite or pitch- 
blende, a source of uranium. It is bivalent, and the chlorides, 
bromides, nitrates, and hydroxides have been studied. 

Radium compounds are luminous, and the active emanations 
emitted by them have been condensed at 150 below zero centi- 
grade, forming new substances, among which helium has been 
identified. The discovery of this fact is responsible for our new 
conception of the divisibility or disintegration of what were 
"once considered indivisible atoms, also of the " smoke ring " 
molecule, and the possible transmutation of the elements. 

Barium, Ba. 

Compounds. — Barium, the next metal to radium in this 
group in point of atomic weight, which is 137.37, occurs chiefly 
as a sulphate BaS0 4 , heavy spar, and BaC0 3 , witherite. Barium 
oxide may be formed by heating the carbonate or nitrate to red 
heat. It absorbs oxygen from the air with formation of the 
binoxide BaCV This in turn is decomposed, oxygen being given 
off and BaO being reproduced. The barium oxide hence be- 
comes a source of oxygen of commercial importance. The cost 
of producing oxygen by this method is obviously small. 

The peroxide of barium is also of particular importance to the 
dentist, in that it is an important source of peroxide of hydrogen. 
This substance is considered more fully in a chapter on mouth 
washes and local anesthetics. (See page 180.) 

Barium hydroxide, BaC^Hs, slightly soluble in water, absorbs 
CO2 very rapidly and may be used as a test for this gas. The 
solution is known as " Baryta Water." 

Analytical Reactions. — Use a 2% solution of the chloride 
for tests. 

BaCl 2 with (NH^CC^ gives white precipitate of barium 



METALS OF GROUP V 7 1 

carbonate. Test solubility in acids. With soluble sulphates 
BaCl 2 produces BaS0 4 insoluble in HC1. (Test for sulphates.) 
BaCl 2 with K 2 Cr 2 7 or K 2 Cr0 4 gives yellow precipitate of 
BaCr0 4 . Barium salts moistened with HC1 and held on a clean 
platinum wire give to the colorless flame of the Bunsen burner 
a green or yellowish-green color. 

Strontium, Sr. 

Atomic weight 87.63. Occurs as the carbonate, SrC0 3 , 
strontianite, also as the sulphate. 

Strontium salts are used commercially in the preparation of 
colored fires, strontium imparting a vivid red color to the flame. 
Strontium oxalate crystallizes in practically the same forms and 
much more easily than calcium oxalate. 

Analytical Reactions. — Use a 3 to 4% solution of the nitrate 
or chloride for tests. 

Sr(N0 3 ) 2 with (NH 4 ) 2 C0 3 gives white precipitate of SrC0 3 . 

Sr(N0 3 ) 2 with H 2 S0 4 or soluble sulphate gives white pre- 
cipitate of SrS0 4 , rather more soluble in water and more slowly 
formed than BaS0 4 . 

A saturated solution of SrS0 4 may be used to test for barium 
in presence of Sr salts. 

Sr(N0 3 ) 2 with K 2 Cr0 4 gives precipitate of SrCr0 4 , but with 
the acid chromate (dichromate) of potassium, K 2 Cr 2 7 , no 
precipitate is formed except in concentrated solutions. 

Sr(N0 3 ) 2 ^with oxalic acid gives a precipitate of strontium 
oxalate, SrC 2 4 , crystallizing in the so-called envelop form (Plate 
II, Fig. 3, page 170). Salts of Sr color the Bunsen flame crimson. 

Calcium, Ca. 

Atomic weight 40.07. Calcium is widely distributed and 
very abundant, limestone, chalk, marble, and calc-spar being 
natural carbonates; CaC0 3 , gypsum, and alabaster are sulphates. 



72 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Calcium phosphate occurs in the mineral apatite and is also 
a principal constituent of animal bones. 

Plaster of Paris. — Calcium sulphate is of particular interest, 
occurring as gypsum, CaS0 4 .2 H 2 0. Upon heating, the two 
molecules of water of crystallization may be driven off, leaving 
the anhydrous CaS0 4 , or plaster of Paris, so largely used in dental 
laboratories. If the heat used is too high a " dead burnt " 
plaster results which unites so slowly with water as to be practi- 
cally useless. More careful dehydration at a lower temperature 
yields a so-called " soluble anhydrite " which absorbs water 
rapidly. The best plaster for dental purposes is neither of these, 
but a product which contains one molecule of water to every two 
of calcium sulphate. This is known as the half hydrate and is 
the chief constituent of plaster of Paris. This half hydrate has 
a property of setting with more or less of a fibrous character 
which permits its use in the formation of plaster casts. Essig 
states that if, in the preparation of plaster, the heat is allowed 
to exceed 127 C, its affinity for water is impaired or destroyed 
and this effect will not be produced.* 

As plaster sets, more or less expansion takes place, and, if 
spread upon glass, the mass usually rises slightly in the center, 
producing a plate which is somewhat concave on the under 
surface. This tendency to expansion varies with different grades 
of plaster, as may easily be shown by a method suggested by 
Dr. George H. Wilson in the Dental Cosmos for August, 1905, 
page 940, which consists simply of filling small glass beakers 
with mixtures similarly prepared. Some samples were found 
to expand so slightly as not to injure the glass, others cracked, 
and some broke the beaker into fragments. 

In the Dental Cosmos for 1908, page 67, Dr. J. H. Prothero 
of Chicago shows that plaster during the first four minutes gives a 
slight contraction, and is then stationary for about forty-five 
seconds. Then it expands with increasing rapidity till the maxi- 

* American Text-book of Prosthetic Dentistry. 



METALS OF GROUP V 73 

mum movement attained is one-thousandth of an inch per minute 
for about ten minutes. After half an hour the movement prac- 
tically ceases. The slightest possible trace of potassium sul- 
phate added to the water used in mixing and the least possible 
agitation reduces both the rate and the amount of expansion. 

The method of mixing also affects the amount of expansion. 
In a valuable article on " Experiments in Plaster of Paris to 
Test Expansions," by Dr. Stewart J. Spence, in Items of In- 
terest, 1902, page 721, it is shown that " not only do different 
plasters expand in differing degrees, but the same plaster expands 
very differently according to the stirring given it before pouring, " 
and that long stirring increases the heat developed, the rapidity 
of setting, and the amount of expansion, but decreases the 
strength. 

Various methods have been prepared to overcome the diffi- 
culties in manipulation of plaster, such as mixing the plaster 
with alum, marble-dust, or potassium sulphate. A compound 
on the market consists of a mixture of plaster and Portland 
cement. A mixture which has been very strongly recommended 
as an investment preparation consists of two-thirds plaster and 
one-third powdered pumice-stone. 

Analytical Reactions. — Use a 3 or 4% solution of CaCl 2 for 
tests. 

CaCl 2 with (NH4) 2 C0 3 gives white precipitate of CaC0 3 , 
easily soluble in acids. 

CaCl 2 with oxalic acid or soluble oxalates gives a white pre- 
cipitate of CaC 2 4 , similar in form to the SrC 2 4 but much more 
difficult to obtain in the crystalline condition. 

CaS0 4 is not precipitated except from moderately concen- 
trated solution. 

A saturated solution of CaS0 4 may be used to test for stron- 
tium salts in presence of Ca. 



74 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Magnesium, Mg. 

The Metal. — Atomic weight 24.32. Principal sources are 
the carbonate, MgC03, magnesite, and a double carbonate, 
CaMg(C0 3 )2, dolomite. The sulphate MgS0 4 occurs in the 
mineral kieserite in the "Stassfurt deposit." " French chalk " 
(or talcum), soapstone, and meerschaum consist of magnesium 
silicate in varying states of purity. 

Asbestos is a double silicate of magnesium and calcium. 

Properties. — Magnesium is a silver white metal occurring 
in trade as ribbon or powder. It burns easily in air, forming 
MgO and traces of Mg 3 N 2 and producing a white light which is 
used in photography. It is a light metal having a specific 
gravity of 1.75. 

Alloys. — For the alloy with aluminium, see page 56. The 
amalgam alloys are not practical as they heat and swell in a man- 
ner which renders them practically useless. 

Compounds. — Epsom salt, or magnesium sulphate, occurs 
as a constituent of laxative waters. The crystallized salt, 
MgS0 4 -7 H 2 resembles oxalic acid in appearance, and has been 
mistaken in several instances for the poisonous acid. 

Magnesium carbonate is used in pharmacy in two forms; 
viz., the light and the heavy. These are produced by precipi- 
tating dilute or concentrated solution of magnesium sulphate 
with sodium carbonate. 

The light and heavy magnesium oxides are produced by 
calcination of the light or heavy carbonates. Magnesium salts 
are quite generally distributed in the human system, but in 
small quantities. They occur in the bones, the teeth, and the 
various body fluids. 

Analytical Reactions. — A five per cent, solution of the 
sulphate or nitrate may be used in the following tests: 

Magnesium salts with (NH^CC^ give a white precipitate 
of basic carbonate of variable composition. This precipitate 



METALS OF GROUP V 75 

forms very slowly in dilute solution, and in the presence of 
NH4CI the formation of soluble double salts prevents the pre- 
cipitation altogether. 

MgCl 2 with Na 2 HP0 4 gives in fairly concentrated solution 
a white precipitate of MgHP0 4 . In presence of NH4CI and 
NH4OH the alkaline phosphates precipitate magnesium-am- 
monium-phosphate, MgNH 4 P0 4 .6 H 2 0, even from very dilute 
solution (Plate IV, Fig. 2). 

In case the precipitate has formed very slowly, it may separ- 
ate as small, almost transparent, crystals clinging to the sides 
of the beaker. 

Ammonium oxalate does not precipitate magnesium solutions. 

Analysis of Group V. 

(Ba, Sr, Ca, Mg.) 

To the filtrate from Group IV containing NH4CI and NH4OH, 
add (NH4) 2 C0 3 . (If NH4CI and NH4OH are not present, add 
10 c.c. of NH4CI solution and NH4OH till strongly alkaline before 
proceeding with the analysis.) Ba, Sr, and Ca will be pre- 
cipitated as carbonates; Mg will be held in solution by the 
ammonium chloride. Filter. 



Ca, Ba, Sr carbonates. 

Mg and metals of Group VI. 



Test the filtrate for Mg by adding Na 2 HP0 4 , when a white 
crystalline precipitate is NH4MgP0 4 .6 H 2 0. 

To the carbonates on the paper add dilute acetic acid, which 
will dissolve the precipitate, forming acetates of the three metals. 




76 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Take a portion of the acetate solution in a test-tube and make 
a preliminary test for Ba by adding acid chromate of potas- 
sium (K 2 Cr 2 7 ). A yellowish precipitate will be BaCr0 4 . 

If Ba is present, add K 2 Cr 2 7 to the whole of the solution 
and filter out the BaCr0 4 . 




BaCr0 4 . 

Sr and Ca acetates, K 2 Cr 2 7 , etc. 



It is desirable to remove the excess of bichromate from the 
filtrate before testing for Ca and Sr.* To do this add NH4OH 
till alkaline; then (NH^COs will precipitate SrC0 3 and CaC0 3 . 
Filter and dissolve off the paper with acetic acid as before. 




CaC0 3 and SrC03, which when treated with acetic 



acid, will give a solution of the acetates of Ca and Sr. 



Reserve about one-fourth of this acetate solution. To the 
remainder add dilute K 2 S0 4 solution, which will precipitate 
SrS0 4 . (If only slight amounts of Sr are present, it may take 
some time to complete the precipitation. If a large amount 

* The object of removing the K 2 Cr 2 7 is to furnish a colorless solution wherein 
the Sr or Ca precipitates may be more clearly discerned. It is not absolutely 
necessary and, in case the amount of Sr and Ca is probably slight, might be omitted, 
as the operation is always attended with some loss. 



METALS OF GROUP V 



77 



of Ca is present, some CaS0 4 may also be thrown down.) 
Filter. 




SrSOi 



Ca(C2H 3 2 )2orCaS04 



Test nitrate for Ca by adding ammonium oxalate, which will 
precipitate calcium oxalate, white. 

If there is any question about the precipitate thrown out by 
K 2 S0 4 being Sr, make confirmatory test on reserved portion, 
either by flame test (page 71), or by adding CaS0 4 , and allowing 
to stand twelve hours. CaS0 4 will precipitate Sr as SrS0 4 , but 
of course cannot precipitate Ca. 

QUESTIONS ON GROUP V. 

Why add NH 4 C1 before precipitating the group with (NH 4 ) 2 
C0 3 ? 

Why dissolve the precipitated carbonates in acetic acid 
rather than HC1? 

Why use the acid chromate of potassium (K 2 Cr 2 7 ) in testing 
for Ba rather than the neutral chromate (K 2 Cr0 4 )? 

Why precipitate Sr and Ca after separation of Ba with 
K 2 Cr 2 7 ? 

OUTLINE SCHEME FOR ANALYSIS OF GROUP V 

To clear filtrate from Group IV add (NHO2CO3. 



Precipitale=Ba, Sr, and Ca. Add K^CnO?, if necessary to pre- 
cipitate Ba. 



Precipitate = BaCr0 4 



Solution «= sr ana ^a. JK.eprecipi- 
tate Sr or Ca with (NH 4 ) 2 C0j. 
Dissolve in HA. Remove Sr 
with K 2 S0 4 and alcohol, and 
test filtrate for Ca with (NH 4 ) 2 
C 2 0, (page 73) • 



Solution=Mg. Test for Mg 
with Na2HP04 (page 75). 



CHAPTER VIII. 
METALS OF GROUP VI. 

The Alkaline Metals, K, Na, NH, Li. 

Potassium, sodium, and the hypothetical " metal" ammo- 
nium are the bases of a very large number of salts used in the 
arts and sciences. 

As a class the metals may be distinguished from the alkaline 
earths by the ready solubility of their hydrates and carbonates. 
The hydrates of the alkaline earths are only sparingly soluble, 
and their carbonates are insoluble. 

- The salts of lithium are also soluble, but are used in relatively 
small amounts. 

These bases are not precipitated by any group reagent and 
must be detected by individual tests. 

Potassium, K (Kalium). 

The Metal. — Atomic weight 39.1. Occurs as carbonate in 
wood ashes, as nitrate in the " niter beds " of India, etc., as 
chloride from the Stassfurt deposit in the Province of Saxony, 
Prussia, as the mineral sylvite, also in the double chloride of 
magnesium and potassium (carnallite). 

Properties. — Melting-point 62. 5 . Potassium is a silver 
white metal. It decomposes water at ordinary temperatures 
evolving enough heat to ignite the liberated hydrogen. 

Compounds. — The salts of potassium are generally soluble 
in water. Among the more important compounds is the hy- 
droxide KOH. This is used very largely as a starting point in 
the preparation of many of the medicinal salts of potassium. It 

78 



METALS OF GROUP VI 79 

may be made by treating potassium carbonate with slaked lime, 
according to the following reaction: 

Ca0 2 H 2 + K2CO3 = CaC0 3 + 2 KOH. 

The carbonate obtained from wood ashes is known as " salts 
of tartar," and in the impure form as pearl ash. Potassium car- 
bonate is also made in large quantities from the native chloride 
found in the Stassfurt deposit. 

The bicarbonate KHCO3, or saleratus, may be obtained by 
saturating the carbonate with C0 2 . 

K 2 C0 3 + C0 2 + H 2 = 2 KHCO3. 

This salt, used in cooking, proves more or less irritating, and has 
been practically replaced by the corresponding sodium salt, 
NaHC0 3 or " cooking soda." 

Potassium nitrate, KN0 3 , also called niter and saltpeter, is 
used in medicine as a diuretic. It gives off oxygen easily, and 
is consequently a good oxidizing agent, and as such is a con- 
stituent of fireworks, gunpowder, etc. 

KNO3 may be prepared from the cheaper sodium nitrate by 
double decomposition with potassium chloride. 

NaN0 3 + KC1 = KNO3 + NaCl. 

Potassium bromide, used as a sedative, may be prepared by 
treating caustic potash, KOH, with bromine. 

6 Br + 6 KOH = 5 KBr + 3 H 2 + KBr0 3 . 

The bromate, KBr0 3 , is separated by crystallization. 

Potassium iodide may be made in a similar manner by sub- 
stituting iodine for the bromine. Potassium iodide is very 
soluble, being dissolved in less than its own weight of water. 
In the laboratory potassium iodide is used as a solvent for iodine, 
and as a reagent. 

Potassium cyanide, KCN, an extremely poisonous compound, 
is used by jewelers for cleaning silver, etc., and in the arts for 
the preparation of double salts used in electro-plating. It is 



80 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

decomposed by C0 2 , forming K 2 G0 3 and liberating hydrocyanic 
acid. 

Potassium ferrocyanide and f erricyanide are considered under 
cyanogen compounds in Chapter XXV. 

Potassium chlorate may be prepared by treating a hot solution 
of the hydroxide with chlorine gas. The reaction is the same as 
that given for the preparation of the bromide, and results in five 
molecules of the potassium chloride to one of the chlorate. 

Potassium sulphide, K 2 S, is soluble in water and, in common 
with other alkaline sulphides, is a solvent for sulphur, thereby 
forming a number of poly sulphides. 

The pentasulphide, K 2 S 5 , is known as " liver of sulphur" or 
sulphuret of potassium. 

Potassium platinic chloride, K 2 PtCl 6 , and potassium acid 
tartrate, KHC 4 H40 6 , are only sparingly soluble and may be 
precipitated by addition to the solution of an equal volume of 
alcohol, in which they are quite insoluble. 

The potassium acid tartrate, or bitartrate, is also called 
cream of tartar, and is used in the manufacture of baking powder. 
This salt separates from wine vats, it being precipitated by the 
alcohol produced during the process of fermentation of the grape 
juice. In this impure form it is known as argols, or crude tartar. 

Analytical Reactions. — The presence of potassium salts 
may be detected spectroscopically or by the violet color given 
to the flame observed through blue glass. Make comparative 
tests with known solutions of sodium and potassium salts, using 
blue glass of sufficient thickness to obscure the yellow (Na) ray. 

Note. — In making the flame test the best results are obtained by evaporating 
a little of the original solution to dryness, moistening with HC1 and then taking 
up on a loop of clean platinum wire. 

The platinic chloride test may be made as follows: 
Add a few drops of HC1 to a little of the solution, then evapo- 
rate to dryness. Keep at a low red heat till all ammonium 
salts have been driven off, cool, and take up in a little (not 



METALS OF GROUP VI 81 

more than 5 c.c.) distilled water. Add a few drops of H 2 PtCl 6 
and about 5 c.c. of alcohol. Set aside for some time. K 2 PtCl6, 
yellow, will crystallize out recognizable under the microscope 
(Plate III, Fig. 3). 

Sodium, Na (Natrium). 

The Metal. — Atomic weight 23.0. It occurs principally as 
chloride in sea-water and in mineral deposits, and to a lesser ex- 
tent as nitrate, Chili saltpeter, and as cryolite, the double fluor- 
ide of aluminium and sodium, (Na 3 AlF 6 ), found in Greenland. 

Properties. — Melting-point 95. 6°. Sodium is a shiny metal 
of cheese-like consistency, easily cut with a knife. It tarnishes 
quickly in the air, with the formation of the hydroxide. Sodium, 
and potassium also, can be distilled in atmospheres which do 
not affect the metal. 

Compounds. — Sodium peroxide, or dioxide, Na 2 2 , may be 
prepared by simply heating metallic sodium in dry air. It is a 
yellowish white powder used somewhat in dental practice for 
the preparation of alkaline solutions of H 2 2 : 

Na 2 2 + 2 H 2 = 2 NaOH + H 2 2 . 

The alkaline peroxide is much more efficient as a bleaching agent 
than the neutral or acid preparations. 

Sodium hydroxide, NaOH, is found in trade in several forms. 
The stick " caustic soda, " used in chemical laboratories, contains 
anywhere from five to thirty per cent, of water. In a powder 
form, less pure than the above, it is known as " concentrated 
lye," Babbitt's potash, etc., and is used for cleaning, and in the 
manufacture of soap. Sodium hydroxide is caustic or escharotic 
in its action upon animal tissue. It may be made experimentally 
by experiment No. 49, page 376. 

Sodium carbonate, Na 2 C03, crystallizes with ten molecules 
of water. In this form it is known as " sal soda," or washing 
soda. It is used as a starting point in the manufacture of other 



82 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

sodium salts. Sodium carbonate is produced from sodium chlo- 
ride by the Le Blanc process, in which the following reactions are 
involved : 

(i) 2 NaCl + H 2 S0 4 = Na2S0 4 + 2 HCL 

(2) Na 2 S0 4 + 2 C = Na 2 S + 2 C0 2 . 

(3) Na 2 S + CaC0 3 = Na 2 C0 3 + CaS. 

The last two reactions are combined in the actual process of 
manufacture, and the mixture of sodium sulphate, carbon, and 
calcium carbonate are heated together with the resulting forma- 
tion of " black ash " from which is produced pure sodium car- 
bonate. 

More recent processes are the Solvay or ammonia process, 
depending on the following reaction: 

NaCl + NH 3 + C0 2 + H 2 = NaHC0 3 + NH*C1, 

and the cryolite process in which the source of the sodium is the 
double fluoride of sodium and aluminum, Na 3 AlF 6 . By this 
process the cryolite is heated with lime, forming calcium fluoride 
and sodium alumina te. 

Na 3 AlF 6 + 3 CaO = 3 CaF 2 + Na 3 A10 3 . 

Note. — According to Remsen the sodium aluminate probably consists of a 
variety similar in composition to the potassium aluminate given on page 57 
(NaA102 and Na 2 until water is added) . 

Sodium bicarbonate, NaHC0 3 , also called cooking soda, is 
largely used like " saleratus " (KHC0 3 ) as a source of carbon 
dioxide in the leavening or aerating of bread. 

Sodium bicarbonate is hydrolyzed by water, i.e., it dissociates 
in solution forming sodium hydroxide and carbonic acid. The 
carbonic acid is a weak acid furnishing very few hydrogen ions, 
while the hydroxide is a strong base. It follows that the reaction 
of such a solution is alkaline to litmus, although the salt answers 
to our definition of an acid salt. This is true of sodium car- 



i 



METALS OF GROUP VI 83 

bonate (the products of hydrolysis being NaOH and NaHC0 3 ), 
and in a similar manner of corresponding potassium salts. 

Sodium chloride NaCl, common salt, exists in sea-water to 
the extent of 2.7%, and is, to some extent, obtained from this 
source, although the greater amount is produced by the salt 
mines. Salt is a constituent of all of the body fluids, and can be 
easily obtained as cubical crystals by the evaporation of urine or 
of dialyzed saliva. 

Physiological, or normal salt solution, contains about 0.7% of 
sodium chloride, and has practically the same osmotic pressure 
as blood. 

The term " physiological " is to be preferred to the term 
" normal," as normal salt solution is also properly applied to a 
solution used in volumetric analysis containing exactly 5.85% of 
sodium chloride (see page 159). 

Sodium nitrate, NaN0 3 , Chili saltpeter, is valuable as a fer- 
tilizer, but too hygroscopic to be used in the same way as potas- 
sium nitrate, in the preparation of gunpowder, fireworks, etc. 

Sodium phosphate, trisodic phosphate, Na 3 P0 4 , is a crystal- 
line salt, soluble in water, but of slight interest in Dental Chem- 
istry. It is easily decomposed by C0 2 , forming Na 2 HP0 4 and 
Na^COs. 

2 Na 3 P0 4 + H 2 + C0 2 = 2 Na 2 HP0 4 + Na 2 C0 3 . 

The disodic phosphate, Na 2 HP0 4 , also called neutral or 
orthosodium phosphate, is the sodium phosphate of the Pharma- 
copoeia. It is faintly alkaline in reaction, and exists in the body 
fluids generally. The alkaline reaction (to litmus) of saliva is, 
in part, due to its presence. 

The acid, or monobasic sodium phosphate, NaH 2 P0 4 , is a 
translucent crystalline salt found to some extent in the body 
fluids, particularly the urine, to the acidity of which it is probably 
a contributing factor, although to a much less extent than was 
formally supposed. 



S4 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Sodium potassium tartrate, KXaC 4 H40 6 , Rochelle salt, is 
used in medicine as a mild laxative. It is the product of the 
double decomposition incident to raising bread with " cream of 
tartar and soda." 

KHQH 4 6 + NaHC0 3 = KNaC^Oe + C0 2 + H 2 0. 

Sodium sulphate crystallized with ten molecules of water 
(Xa2SO4.ro H 2 0) is known as Glauber's salt. 

Analytical Reactions. — Xa may be detected by the use of the 
spectroscope or by the persistence of the yellow flame obtained 
with a clean platinum wire and a colorless Bunsen flame. Make 
a comparative test with small amount of known sodium salt. 

Sodium salts are soluble with 
only a very few exceptions. The 
pyroantimonate, Xa2H 2 Sb 2 07, may 
be precipitated in the cold by a 
freshly prepared solution of potas- 
sium pyroantimonate. (Prescott 
and Johnson, page 228.) 

From a solution stronger than 
3% and nearly neutral the double 
acetate of uranyl and sodium 

Uranyl Sodium Acetate. (NaC 2 H 3 2 ,U0 2 (C 2 H 3 2 ) 2 ) may be 

precipitated. (Fig. 6.) As triple crystalline acetates may also 
be formed with Mg, Cu, Fe, Xi, and Co, it is recommended to 
first precipitate the bases of the first five groups and drive off 
ammonium salts, as in the test for K with H 2 PtCl 6 .* 

Lithium, Li. 

Atomic weight 6.94. The carbonate, citrate, bromide, and 
chloride are used in medicine. 

The value of lithium salts as uric acid solvents is question- 
able, because of the insolubility of the phosphate (page 242). 
* Behrens's Manual of Microchemical Analysis, page 32. 




METALS OF GROUP VI 85 

The presence of lithium is easily shown after the precipitation 
of strontium by the intense carmine color given to the Bunsen 
flame. 

The spectroscope furnishes a very delicate and positive test 
for this element. 

Ammonium, NH4. 

Ammonia is obtained in large part from the ammoniacal 
liquor of the gas works, where illuminating gas is made by the 
distillation of coal. The liquor, charged witri ammonia, is 
treated with hydrochloric or sulphuric acid, thus producing an 
impure salt which is subsequently purified or used as a source 
of NH 3 in the preparation of pure ammonium compounds. 

•(NEQ2SO4 + Ca0 2 H 2 = CaS0 4 + 2 NH 3 + 2 H 2 0. 

Compounds. — Ammonium hydroxide, NH4OH, has never 
been separated as such, free from water. It undoubtedly ex- 
ists, however, in aqueous solutions of ammonia gas. 
NH 3 + H 2 = NH4OH. 

The negative hydroxyl ions of this ammonium base are not 
separated by dissociation to the same degree as those of potas- 
sium hydroxide in solution; hence, it is a weaker base. 

Aqua ammonia of the pharmacopeia contains 10% NH 3 . 
The " stronger water of ammonia " contains 28% of the gas, 
which is about as strong a solution as it is safe to make for 
shipment, and containers should never be more than four- 
fifths full. The 28% solutionis referred to as 26 ammonia,' the 
degree indicating the specific gravity as taken by the Baume 
-hydrometer. 

Ammonium carbonate exists in solution. The salt used in 
medicine under this name is really a mixture of ammonium 
bicarbonate, NH4HCO3, and the carbamate, NH4NH 2 C0 2 . 

This salt gives off NH 3 gas, and moistened with ammonia 
water and perfumed constitutes " smelling salts." 



86 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Ammonium chloride, sal ammoniac (NH4CI), white, crystal- 
line, is made by neutralizing NH4OH with hydrochloric acid. 
Ammonium chloride will sublime unchanged. It is freely sol- 
uble in water, its solution acts as an electrolyte and will 
dissolve metals from an alloy. If a silver spoon or a ten cent 
piece is allowed to remain for ten or twelve hours in a dilute 
solution of ammonium chloride, an appreciable amount of copper 
will pass into solution, coloring it blue or green, according to the 
concentration of the copper solution. It also dissolves some 
metallic oxides, as zinc oxide. 

As saliva is known to contain considerable NH4CI, the above 
facts should be studied carefully in considering the action of 
saliva on substances used for tilling teeth, although the solvent 
action of NH4CI in saliva is nothing like what it is in water. 

Ammonium nitrate, NHiNOs, crystallizes in large six-sided 
prisms without water of crystallization. It is very soluble in 
water. It melts at 165 C. Heated to 210 C, it decomposes 
into nitrous oxide and water. Above 250 C, other oxides 
of nitrogen are produced, so in the preparation of nitrous oxide 
for dental anesthesia, care should be taken to keep the tem- 
perature of the reaction between these limits. 

Ammonium acetate, NH4C2H3O2. A solution of this salt, 
containing about 7%, is used in medicine as a diaphoretic. 
The solution is also known as Spirit of Mindererus. In analyti- 
cal chemistry, it is used as a solvent for lead sulphate. 

Ammonium sulphate, (NH^SO^ is a white crystalline salt 
soluble in water, not used medicinally, but largely used as a 
reagent in physiological chemistry. It melts at 140 C, and 
at a higher temperature it decomposes. 

Ammonium sulphide, (NH^Sjisused as a solvent and reagent. 
It may be prepared by saturating ammonia water, NH4OH, 
with H 2 S, then adding an equal volume of ammonia water: 

NH4OH + H 2 S = NEUSH + H 2 0, 
and NH4SH + NH40H = (NH^S + H 2 0. 



METALS OF GROUP VI 87 

A poly sulphide, made by dissolving sulphur in (NH 4 ) 2 S is 
the reagent used in dissolving the sulphides of Group II (b) and 
in precipitating the zinc group. 

Ammonium phosphates. Ammonium, like other univalent 
bases, is capable of forming, with phosphoric acid, three differ- 
ent salts. (NEL^PC^ is very unstable. The diammonium phos- 
phate has been used, to a slight extent, in medicine (Br. P.) and 
has been shown to be an energetic activator of lactic acid organ- 
isms.* 

The importance of this fact, in relation to dental caries, has 
yet to be demonstrated. 

Microcosmic salt is a name given to a double ammonium 
sodium phosphate (NP^NaHPC^I^O) used in blowpipe 
analysis. 

Analytical Reactions. — Ammonium salts are generally sol- 
uble. H 2 PtCl 6 precipitates the double chloride (NH 4 )2PtCl 6 , 
similar in appearance and crystalline form to the corresponding 
potassium salt (Plate III, Figs. 1-3). 

Ammonium salts are most easily detected by the evolution 
of ammonia gas (NH 3 ) whenever they are heated with fixed 
alkali, NaOH or KOH. 

The test may be made upon the original solution by boiling 
in a test-tube with a little 10% NaOH, and the escaping NH 3 
may be detected by the odor or, better, by suspending in the 
upper part of the tube a piece of moistened red litmus paper, 
which is promptly turned blue by the " volatile alkali." The 
litmus-paper test is more delicate than the odor test. Care 
should be taken that the paper does not touch the sides of the 
tube, as it may come in contact with traces of NaOH. 

Many ammonium solutions give off NH 3 gas without the aid 
of any fixed alkali. Common examples are the carbonate, acid 
carbonate, hydrate, sulphide, and sulph-hydrate. 

* Dr. Percy Howe in Dental Cosmos. Jan., 191 2. 



88 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

QUESTIONS ON GROUP VI. 

Why use alcohol in the precipitation of ammonium or potas- 
sium as double chloride with platinum? 

Why are the flame tests preferably made with chlorides of 
the metals? 

Why is ammonia called the volatile alkali, and what are the 
fixed alkalis from which it is thus distinguished? 

Analysis of Groups in, IV, and V. 

(When phosphates, borates, or oxalates are present.) 

To the filtrate from Group II add NH 4 C1 and NH4OH in 
slight excess. Heat to boiling and add (NEL^S slowly (always 
keeping the solution at the boiling-point) until precipitation is 
complete. Filter as rapidly as possible and wash with hot water, 
adding occasionally a little (NEL^S. 

The filtrate, which may contain the barium and potassium 
groups, must be concentrated by evaporation, filtered if neces- 
sary, and set aside.* The precipitate may contain MnS, ZnS, 
CoS, NiS, FeS, Al(OH) 3 , and Cr(OH) 3 with phosphates or 
oxalates soluble in acids only. The color of the precipitate 
will give some indication of what is present. Test the pre- 
cipitate for Mn by fusing a part with KNO3 and Na 2 C03. 

Treat the precipitate with cold dilute HC1 in which CoS and 
NiS alone are insoluble. Filter. Treat insoluble residue for 
Co and Ni according to directions on page 67. 

The HC1 solution, which may contain Mn, Zn, Fe, Cr, and 
Al as chlorides, and phosphates and oxalates soluble in acids, and 
which is green or violet if much Cr is present, is boiled with a 
few drops of HN0 3 until all the H 2 S is expelled. 

Test a small portion of the solution for Fe exactly as in 

* If Ni is present, the filtrate is frequently brown or black, since NiS is some- 
what soluble in an excess of (NHO2S, especially if much NHtOH is present. The 
NiS may be precipitated, after evaporation, by acidifying with HC1. 



METALS OF GROUP VI 



8 9 



analysis of Group III given on page 59. Of the remainder of 
the solution take about one-third, and add dilute H 2 S0 4 . 

A white precipitate may contain BaS0 4 , SrS0 4 , and possibly 
CaS0 4 . Filter, wash precipitate, and fuse with a mixture of 
Na 2 C0 3 and K 2 C0 3 . 

Note. — The mixture of the two carbonates in molecular proportions fuses at 
a lower temperature than either salt alone. 

Filter and wash the carbonates thus formed, dissolve them in 
acetic acid and examine this solution for Ba, Sr, and Ca as di- 
rected under the Ba group. To the filtrate from the precipitate 
produced by H 2 S0 4 , or to the solution in which H 2 S0 4 has failed 
to give a precipitate, add three times its volume of alcohol; 
Ca, if present, is precipitated as white CaS0 4 , and its presence 
may be confirmed by dissolving the precipitate in water and 
adding (NH 4 ) 2 C 2 4 , which precipitates CaC 2 4 , white. 

To the rest of the HC1 solution add ferric chloride, carefully, 
till a drop of the solution gives, when mixed with a drop of am- 
nionic hydrate, a yellowish precipitate. To the solution add 
Na 2 C03 or K 2 C03 till the acid is nearly neutralized, then add 
excess of freshly precipitated BaC03, and allow to stand over 
night. Filter. 




Cr and Al as hydrates. (Fe as phosphate or hy- 
drate and BaC0 3 .) 

|_ MnCl2, ZnCl2, and possibly members of Group V. 



Transfer the precipitate to a small beaker and boil for some 
time with NaOH or KOH. The Al will be converted into the 
aluminate KA10 2 . The phosphate will be more or less com- 
pletely changed to potassium or sodium phosphate. Filter. 



go SALTS OF THE METALS AND QUALITATIVE ANALYSIS 




Cr(OH) 3 , BaCO, etc. 
KAIO2 and Na 2 HP0 4 . 



Test precipitate for Cr as on page 58. Add HN0 3 to filtrate 
till acid, then divide into two parts; test one for P 2 5 with 
(NH4) 2 Mo0 4 . 

Test the other for Al by adding NH 4 OH till alkaline, when 
precipitate will be A1P0 4 , insoluble in acetic acid. 

To the solution of Mn and Zn chlorides add a little HC1 and 
boil. Then make alkaline with NH4OH, add (NH 4 ) 2 S, warm 
slightly and filter. The precipitate (MnS and ZnS) may be 
dissolved in cold dilute HC1 and tested for Mn and Zn as in 
analysis of Group IV, page 67. 

OUTLINE SCHEME FOR ANALYSIS OF GROUPS III, IV, AND V. 

(Phosphates, oxalates, borates, etc., being present.) 
To nitrate from Group II add NH4CI and NH4OH. Heat and add (NH 4 ) 2 S. 
Filter rapidly. 



Precipitate=UnS, ZnS, CoS, NiS, FeS, Al(OH)i, Cr(OH) 3 , also phosphates, etc., 
soluble in acids only. Fuse part of precipitate and test for Mn (page 63). Treat 
remainder c cold dilute HC1. 


Filtrate, 
members of 
Ba and K 






groups 


Residue= 

CoS and 

NiS. Make 


Solution =Mn, Zn, Cr, and Al. Divide solution into three parts of 
about 1/8, 2/8, and 5/8, respectively, and treat as follows: 




borax-bead 
test and 


I. 




III. 


separate Co 
if neces- 
sary, c 
KNO2 
(page 67). 


Test 

small 

portion 

forFe 

(page 55). 


II. 
To second portion add di- 
lute H2SO4. 


To third portion add FeCh to combine 
c H3PO4, etc., then add NasCOs or 
K2CO3, and BaC0 3 (page 89). 














Precipitate 
may be 
BaS0 4 , 
SrSO* or 
CaS0 4 . Fil- 
ter, wash, 

fuse c 
Na 2 C0 3 and 
K2CO3. Dis- 
solve fusion 
in HA and 
analyze for 
Group V. 


Solution^ 
CaSO*. 

Add alco- 
hol; if pre- 
cipitate oc- 
curs, filter, 
dissolve in 

H2O, and 

test with 

ammonium 

oxalate. 


Precipitate ■= Cr, Al, Fe, and 
BaC03. Boil precipitate 
c NaOH and filter. 


Solution = 

Mn and Zn. 

Reprecipi- 

tate Mn 




Residue = 
Cr, BaC0 3 , 

etc. Test 

for Cr as on 

page 59- 


Solution = 

KAIO2. 

Test for Al 

as on page 

59- 


and Zn as 
sulphides, 
and test 
according 
to page 67. 



CHAPTER IX. 

ANALYTICAL REACTIONS OF THE ACIDS. 

In the analytical processes thus far described we have con- 
sidered only the separation and detection of the basic or metallic 
part of the salt (positive ions), that is, we have analyzed a 
solution of ferric chloride, and found the iron only. It is neces- 
sary to find the chlorine (negative ion). Before making any 
examination for negative ions, it will be possible to save a con- 
siderable amount of both time and labor by first carefully con- 
sidering what acids are capable of forming soluble salts with the 
bases which have already been detected. To facilitate this 
consideration a table of solubilities will be found below and on 
the following page, by a careful study of which it will be possible 
to select such acids as are most likely to be present in the un- 
known solution under investigation, and also to neglect a num- 
ber of acids which, from the solubility of their salts, together with 
the character of the solution (acid, alkaline, neutral and aqueous, 
or otherwise), will necessarily be absent. 



TABLE 


SHOWING 


THE SOLUBILITY 


OF 


SALTS 








K 


Na 


NH 4 


Mg 


Ba 


Sr 


Ca 


Mn 


Zn 


Co 


Ni 


Fe 


Fe 2 




w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 


w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 


w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 

w 

w 
w 
w 
w 


w 

a 
a 

wa 
w 
a 
w 
w 
w 
w 
w 
w 
a 
a 
a 
a 
w 

wa 
w 

wa 


w 
a 

wa 
a 
w 
a 
w 
w 
a 

wa 
w 
w 
a 
w 
a 
a 

w 
w 
a 


w 
a 

wa 
a 
w 
a 
w 
w 

wa 
w 
w 
w 

w 
a 
a 

w 
w 
a 


w 
a 
a 

w 
a 
w 
w 

wa 
w 
w 
w 
a 
w 
a 
a 

wi 
w 
w 
a 


w 
a 

w 
a 
w 
w 
w 
a 
w 
w 
a 
a 
a 
a 
w 
a 
w 
wa 


w 
a 

a 
w 
a 
w 
w 
w 
a 
w 
w 
a 
a 
a 
a 
w 
a 
w 
a 


w 
a 
a 
a 
w 
a 
w 
w 
a 
ai 
w 
w 
a 
a 
a 
a 
w 
a 
w 
w 


w 
a 
a 
a 
w 
a 
w 
w 
a 
ai 
w 
w 
a 
a 

a 
w 
a 
w 
a 


w 
a 
a 
a 

w 
a 
w 
w 

ai 
w 
w 
a 
a 
a 
a 
w 
a 
w 
wa 




Arsenate 

Arsenite 

Borate 


a 
a 
a 


Carbonate 

Chlorate 

Chloride 


a 

w 


Chromate 

Cyanide 


w 


Iodide 




Nitrate 


w 


Oxide 




Phosphate 




Silicate 












Sulphocyanate 

Tartrate 


w 







91 



92 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 



TABLE SHOWING THE SOLUBILITY OF SALTS. - 


-CONCLUDED. 




Cr 2 


All 


Sb 


Sn" 


Sn ,v 


Au 


Ag 


Hg 2 


Hg 


Pb 


Bi 


Cu 


Cd 




w 
a 

a 
w 

w 
w&i 

a 

a 

w 

w 

w 
a&i 

a 

a 
w&a 

w 
w 


w 
a 

a 

w 

w 
w 

w 
w 
a 
a&i 
a 
ai 
w 

w 


w 
a 
a 

wa 

wa 
a 

wa 

a 
a 
a 

a 
a 

w 


w 
a 
a 
a 
w 

w 
w 
a 

w 
a 
a 
a 
a 

w 
a 

wa 


w 

a 
a 

w 

w 

w 
a 
w 
a& i 
a 

w 
a 

w 


w 

w 
w 

a 


wa 
a 
a 
a 

a 

w 

a 
i 

w 
a 
a 
a 

wa 
a 
i 
a 


wa 
a 
a 

ai 
a 
w 
ai 
a 

a 
w 
a 
a 
a 

wa 
a 
a 
a 


w 
a 
a 

wa 
a 
w 
w 

wa 
w 
a 
w 
a 
a 
a 

wa 
a 

w 
a 


w 

a 

a 

a 
wi 

a 

w 

wi 

ai 

a 
wa 

w 

a 

a 

a 

a 

a 
a 
a 


w 
a 

a 
wa 

a 

w 
wa 

a 
wa 

a 

a 

a 

a 

a 

a 
a 

a 


w 
a 
a 
a 
w 
a 
w 
w 
w 
a 
a 
w 
a 
a 
a 

w 
a 
a 
wa 




























Chloride 
















Nitrate 








Oxide 








Silicate 


a 






Sulphocyanate 


wa 







w, soluble in water; a, insoluble in water, soluble in acids; i, insoluble in water or acids; wa, 
sparingly soluble in water, readily soluble in acids; wi, sparingly soluble in water and acids; ai, 
sparingly soluble in acids only. 

In this connection it is well to remember that practically all 
nitrates and chlorates are soluble in water; sulphates are mostly 
soluble, except those of barium, strontium, and calcium. Phos- 
phates (di- or trimetallic), silicates, oxalates, and borates are 
practically insoluble, except those of the alkaline metals. This 
latter statement is also true of carbonates, except that some of 
the carbonates will dissolve to an appreciable extent in water 
containing carbon dioxide. Chlorides, bromides, and iodides 
are nearly all soluble except those of the first-group metals. 
Sulphides are insoluble except those of Groups V and VI. Acid 
salts are usually more soluble than neutral salts. 

In making qualitative tests for the negative ions it is not 
necessary to separate them one from the other, as it is in the 
case of metals; hence the tests are individual ones, usually made 
upon the original substance or solution, and often require con- 
firmation before conclusive evidence is obtained. The grouping 
is, therefore, simply for convenience, as it thus becomes possible 
to exclude a considerable number of acids by a single general test. 



ANALYTICAL REACTIONS OF THE ACIDS 93 

Acid Groups (negative ions). 

Group I may include such acids as give effervescence when 
their dry salts are treated with dilute H 2 S0 4 , as H 2 C0 3 , H 2 S, 
H 2 S 2 3 , H 2 S0 3 and HCN. 

Group II may include acids giving a precipitate with AgN0 3 
in dilute HN0 3 solution, as HC1, HBr, HI, HCN, HCNS, HN0 2 , 
HCIO, H 4 FeCy 6 , H 3 FeCy 6 , H 2 S 2 3 , H 2 S and HPH 2 2 . 

This second group may be further subdivided into three parts 
according to the color of the precipitate obtained (pages 95 and 

97)- 

Group III may include acids forming insoluble salts with 
BaCl 2 or CaCl 2 and not found in Groups I or II, as H 2 S0 4 , H 2 C 2 4 , 
H 3 P0 4 , H 3 B0 3 , H 2 Cr0 4 and H 2 Si0 3 . 

Group IV: We may put in Group IV any acids not included 
in the foregoing groups. Of common occurrence are nitric 
(nitrates), chloric (chlorates), and acetic (acetates). 

Detection of Acids of Group I. 

(Acids effervescing with dilute sulphuric acid. H 2 C0 3 , H 2 S, H 2 S0 3 , H 2 S 2 3 , HCN.) 

To a test-tube a quarter full of the unknown solution, or a 
little dry substance on a watch-glass, add dilute H 2 S0 4 . If 
solution is very dilute, concentrate it before making test, as a 
slight amount of gas might be absorbed by the water. Watch 
carefully for any escape of gas and note any odor which may be 
given off. 

Carbonates evolve C0 2 , odorless, but if passed into lime-water 
or baryta-water will give white precipitate of CaC0 3 or BaC0 3 . 

Sulphides evolve H 2 S, odor of rotten eggs. Confirm by 
adding a little dilute H 2 S0 4 to the suspected powder (or solu- 
tion) in a test-tube and holding over the mouth of the tube a 
piece of filter-paper wet with a solution of lead acetate. The 
test-tube may be warmed slightly to expel the gas, when a dark- 



94 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

colored stain will appear on the filter-paper, due to the formation 
ofPbS. 

Sulphites evolve S0 2 , odor of burning sulphur. Sulphites 
in neutral solution may be further identified by the deep-red 
color produced with ferric chloride. The color is discharged 
upon addition of dilute acids, HO, or H 2 S0 4 (difference from 
HCNS). 

Thiosulphates also evolve S0 2 , but at the same time the 
mixture becomes cloudy from precipitation of sulphur.* 

Thiosulphates in neutral solution treated with ferric chloride 
give a violet to purple color, fading (rapidly upon warming) to 
a colorless solution. In mixtures of sulphites and thiosulphates 
both acids may often be detected by the use of FeCl3, the deep- 
red coloration of the mixed acids rapidly fading to the lighter red 
of Fe 2 (S0 3 )3 (not to colorless solution). 

Cyanides evolve HCN, odor of peach-stones. (Mercuric 
cyanide does not respond to this reaction.) Confirm by reactions 
given under Group II. 

Preliminary Tests for Common Acids of Groups 11 and in. 

(In preparatory courses the acids given in this list may be sufficient.) 

From the acids of Group II and III it may be desirable to 
select for laboratory practice, at least at the beginning of the 
acid work, the more common members of the groups. These 
will be HC1, HBr, HI, HCN, and H 2 S of Group II and H 2 S0 4 , 
H 2 C 2 4 , and H 3 P0 4 of Group III; and tests for them may be 
made as follows: 

Chlorides give with AgN0 3 in presence of HN0 3 a white 
curdy precipitate of AgCl, much more freely soluble in ammonia 
than any other acid of the group here given except the cyanide 

* Sulphides may also precipitate sulphur in presence of compounds capable of 
oxidizing the H2S, such as FeCls. In the absence of sulphates either H 2 S0 3 or 
H2S2O3 can be oxidized to H 2 S0 4 by heating with HNO3 and a precipitate of BaS0 4 
obtained with BaCk 



ANALYTICAL REACTIONS OF THE ACIDS 95 

AgCN, but HCN is a member of the first acid group and would 
have been previously detected. 

Bromides with AgN0 3 and HN0 3 give a precipitate of AgBr 
similar in appearance to AgCl, but with a slightly yellowish 
color and only sparingly soluble in NH4OH. 

The tests, described on page 97, should also be made if 
bromides or iodides are suspected in the solution. 

Cyanides, see Group I. 

Sulphides will give a black precipitate with AgN0 3 , and 
have been previously considered in Group I. 

Sulphates may be detected by first acidifying the solution 
strongly with HC1 (filtering out a precipitate if any occurs) 
ard adding a solution of BaC^; a white precipitate will then be 
BaS0 4 , showing presence of sulphates in solution tested. 

Phosphates in a solution containing HN0 3 and free or nearly 
free from HC1 will give, with ammonium molybdate, a yellow 
crystalline precipitate of ammonium phosphomolybdate. 

Oxalates may be detected, in a solution free from sulphates 
and which is slightly acid with acetic acid, by simple addition 
of calcium chloride, which will precipitate CaC 2 4 , white and 
crystalline. 

Detection of Acids of Group II. 

(Giving precipitate with AgN0 3 in presence of dilute HN0 3 .) 

To the solution to be tested add a very slight amount of 
HNO3 and a few cubic centimeters of AgN0 3 solution. A pre- 
cipitate indicates acids of this group. 

(a) If the precipitate is white, the presence of chlorides (HC1), 
cyanides (HCN), sulphocyanates (HCNS), ferrocyanates 
(H^FeCyg), hypochlorites (HCIO),* or nitrites (HN0 2 ) is in- 
dicated. 

* Precipitate is AgCl. Reaction is 3 NaCIO + 3 AgN0 3 = 2 AgCl + AgClOi 
+ 3 NaN0 3 . 



96 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

To separate or identify these silver precipitates allow to 
settle, decant the supernatant fluid, and add NH4OH. Shake 
thoroughly, when the chloride (AgCl), cyanide (AgCN), and 
nitrite (AgN0 2 ) will dissolve easily, the sulphocyanate (AgCNS) 
and the ferrocyanide (Ag 4 Fe(CN) 6 ) slowly or slightly. 

If KCNS, or H 4 Fe(CN) 6 is indicated, test original solution 
with a few drops of FeCl 3 . Sulphocyanates or thiocyanates 
(HCNS) give a deep blood-red solution. The color is soluble 
in ether and may be discharged by HgCl 2 . Ferrocyanides 
(H 4 Fe(CN) 6 ) give a deep-blue precipitate. (See page 55.) 

Acids forming white silver precipitates, easily soluble in 
ammonia, may be distinguished as follows: 

Chlorides (HC1) may be distinguished from HBr and HI 
by the ready solubility of the silver precipitate in NH 4 OH. If 
bromides and iodides are present, liberate the halogens by means 
of MnO-2 and H 2 S0 4 and pass the mixed gases into a solution of 
aniline in acetic acid (4 c.c. of saturated aqueous solution of 
aniline and 1 c.c. glacial acetic acid). Iodine gives no precipi- 
tate, bromine gives a white one and chlorine a black one. (Pres- 
cott and Johnson, page 336.) 

This is a delicate and very satisfactory test for bromine but 
not so delicate for chlorine in the presence of bromides. For 
such cases the following cldoro-chromic anhydride test is recom- 
mended. Neutralize the solution if necessary, evaporate to 
dryness, transfer residue to a test-tube of rather small diam- 
eter, add a little solid K 2 Cr 2 07, then concentrated H 2 S0 4 . De- 
cant the fumes into a wider test-tube containing a few cubic 
centimeters of NH 4 OH. 

If the chloro-chromic anhydride is evolved, ammonium 
chroma te will be formed. Test by making acid with acetic 
acid, then adding acetate of lead. A yellow precipitate of lead 
chromate indicates chlorine in the original solution. 

Hypochlorites liberate I from KI without the addition of 
acid. 



ANALYTICAL REACTIONS OF THE ACIDS 97 

Note. — Hypochlorite solutions are usually quite strongly alkaline, and in such 
cases a considerable amount of iodide is necessary to obtain the characteristic color 
in chloroform or with starch. 

Nitrites liberate I from KI after the addition of acetic acid. 
They also give a brown coloration with acetic acid and a crystal 
of ferrous sulphate. (Nitrates require a stronger acid.) 

Note. — This test is much more delicate than either of the others given, and 
if the solution is very dilute it is well to make it, even if the indigo color is not 
discharged. ', 

Further mix a little of the solution with a few cubic centi- 
meters of dilute indigo solution and shake. The indigo is de- 
colorized by either hypochlorites (HCIO) or by nitrites (HN0 2 ) . 

Cyanides may be tested for as under Group I. If this test is 
not conclusive, they may be converted into sulphocyanides by 
the addition of a few drops of (NH 4 ) 2 S and evaporation on the 
water-bath to dryness. It may then be dissolved in a little dis- 
tilled H 2 0, filtered and tested with FeCl 3 . 

(b) The precipitate is red-brown or orange, soluble in 
NH4OH = H 3 FeCy 6 . Ferricyanide indicated. 

(c) The precipitate is black or turns black upon warming: 
H 2 S turns black immediately. HH 2 P0 2 starts to precipitate 
white, but rapidly turns black, H 2 S 2 3 precipitates white and 
turns black slowly or upon heating. 

Sulphides (H 2 S) and thiosulphates (H 2 S 2 3 ) may also be 
detected as described under Group I, Acids. 

(d) If the precipitate, originally obtained, is yellow and in- 
soluble in NH4OH, iodides are indicated; if yellowish white and 
slowly soluble in NH4OH, bromides are probably present. 

Iodides and bromides (HI and HBr) may be detected in 
the same solution by adding chlorine water, very cautiously at 
first, and shaking with chloroform. The chlorine liberates the 
iodine, which is dissolved by the chloroform with violet color. 
Excess of chlorine decolorizes the iodine and liberates the bromine 
which, in turn, is dissolved by the chloroform with yellow to 
red color. 



oS SALTS OF THE METALS AXD QUALITATIVE ANALYSIS 

Acid Group III. 

Is forming insoluble barium or calcium salts, not included in the Acid 
Group I or II.) 

The members of this group may be separated from each 
other, although this is not necessary unless several members 
are present. H 2 S0 4 , H 2 C 2 4 , H 2 Cr0 4 , H 2 Si0 3; H3BO3, H 3 P0 4 , 
separated as follows: To a little of the unknown solution add 
2 or 3 c.c. of HC1; a white or gelatinous precipitate which is not 
dissolved by dilution with water and warming is probably silicic 
acid. Make a bead test with microcosmic salt; the particles of 
Si0 2 remain undisturbed by the hot bead, forming the so-called 
silicon " skeleton.'' Filter out the silicic acid and add CaCl 2 
or a mixture of BaCl 2 and CaCl 2 ; a white precipitate will be 
BaS0 4 * (test for sulphates), the Ba and Ca salts of all remain- 
ing acids of the group being soluble in HC1. 

Filter out the BaS0 4 , and to the filtrate add XH 4 OH, which 
will cause a precipitate of barium oxalate, chr ornate, borate, and 
phosphate. Filter, wash precipitate two or three times, reject 
wash-water, then transfer to test-tube by making a small hole in 
point of paper and forcibly washing through with the least pos- 
sible amount of water; acidulate strongly with acetic acid, which 
will dissolve the phosphates and borates, leaving undissolved 
the oxalates (BaC 2 4 , white) and chromates (BaCr0 4 . yellow. 



Oxalic and chromic acids as barium salts. 
Phosphoric and boric acids. 



* If the HC1 is too strong, BaCb may be precipitated as such, but the pre- 
cipitate in this case will form more slowly than the BaS0 4 ; it will have a crystal- 
line appearance and will dissolve upon addition of water. 




ANALYTICAL REACTIONS OF THE ACIDS 99 

Divide the filtrate into two parts, (a) and (6). Test one 
part, (a), for H3P0 4 by adding to it an excess of ammonium 
molybdate* (in HN0 3 ), when a yellow precipitate (forming 
sometimes after several hours' standing) is ammonium phospho- 
molybdate (test for phosphates); the mixture may be warmed 
to hasten precipitation; the degree of heat should not exceed 
40 C, as the ammonium molybdate might be decomposed, 
giving a yellow precipitate similar to the phosphomolybdate. 

Note. — If As is present, it must be removed by H 2 S before testing for H3PO4. 

Test the other part, (6), for H3BO3 by evaporating to dryness 
in a porcelain dish; then moisten with strong H 2 S0 4 , cover with 
a little alcohol, and ignite. Boric acid will give to the flame 
(particularly the edge) of the burning alcohol a green color due 
to formation of ethyl borate. This color is more easily apparent 
if the dish is placed in a darkened corner. 

A test for H3BO3 may also be made with turmeric paper, 
which if dipped into a solution of boric acid, or of a borate mixed 
with HC1 or H 2 S0 4 to slight but distinct acid reaction, and dried 
at ioo°, becomes red; the red color becomes bluish black or 
greenish black when moistened with a solution of an alkali or 
an alkaline carbonate. If there is a suspicion that H 2 Cr0 4 and 
H 2 C 2 4 are both present, dissolve the precipitate of barium 
oxalate and chroma te off the paper with dilute HO; divide the 
filtrate into two parts and test one for H 2 Cr0 4 by addition of 
H 2 2 , which with chromates in presence of HC1 produces a deep- 
blue solution and ultimately CrCls. 

In the absence of chromates, the precipitate being white, 
oxalates may be confirmed by coloring the second part of the 
solution a faint pink with a dilute solution of KMn0 4 and warm- 
ing, when the color will be discharged. 

In the presence of chromates, the precipitate being yellow, 
it will be necessary to test the original solution for oxalates 

* Preparation of ammonium molybdate solution, appendix, page 424. 



IOO SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

as follows: To a few centimeters of the unknown add alcohol; 
warm. The chromate will be reduced to CrCl 3 . Add NH 4 OH 
till alkaline and filter out the precipitate, Cr(OH) 3 . The filtrate 
may be tested for oxalic acid as above, or with CaCl 2 , a white 
precipitate being CaC 2 4 . 

Acids of Group IV. 

The remaining acids of importance not included in either 
of the three preceding groups are nitric, HN0 3 , chloric, HC10 3 , 
and acetic, HC 2 H 3 2 . 

Nitrates. — Saturate 5 c.c. of a very dilute nitrate solution 
with FeS0 4 . Filter and carefully underlay the clear filtrate 
with concentrated sulphuric acid; a dark ring (pale red-brown 
to nearly black) at point of contact of the two liquids shows 
presence of a nitrate. 

Chlorates. — A solution free from chlorides or hypochlorites 
treated with Zn and dilute H 2 S0 4 will give a test for HC1 if 
chlorates were originally present, the chlorate having been re- 
duced by the nascent hydrogen: 
2 KCIO3 + 6 Zn + 7 H 2 S0 4 = 6 ZnS0 4 + K 2 S0 4 + 2 HC1 + 6H 2 0. 

Boiling with sulphurous acid also reduces HC10 3 (and HCIO) 
toHCl. 

If the substance is in solid form, a very small particle may 
be warmed with concentrated H 2 S0 4 . Chlorates detonate and 
give off yellow fumes of C10 2 : 

3 KCIO3 + 2 H 2 S0 4 = 2 KHS0 4 + KC10 4 + 2 C10 2 + H 2 0. 

Acetates give with ferric chloride a red color which is not 
discharged by HgCl 2 (difference from sulphocyanate) , but may 
be discharged by HC1 (difference from sulphocyanate and 
meconate). 

A more positive test is the formation of the ethyl ester or 
acetic ether. A blank test for comparison should always be 
made, the method of procedure being as follows: 



ANALYTICAL REACTIONS OF THE ACIDS IOI 

Take two test-tubes of practically equal diameter, mix in 
each equal volumes of alcohol and strong sulphuric acid; warm 
the tubes together; then into one introduce a few centimeters 
of the unknown solution, and into the other an equal volume of 
water. Heat again to a boiling-point and compare the odors from 
the two tubes. The acetate is easily detected if present. 



CHAPTER X. 
ANALYSIS IN THE DRY WAY. 

In the examination of solid substances much may be learned 
by a few simple tests directly applied to the substance, which 
has been reduced (if necessary) to the form of a powder. 

Some of these are usually used as preliminary to the solu- 
tion of the substance and regular analysis in the wet way. These 
tests may be made quickly, and, with a little elaboration, will 
often give all the information required regarding an unknown 
substance. 

The practical questions of actual experience are usually 
simple ones. It is not an analysis of an unknown solution 
possibly containing all the metals of one or more groups that 
interests an active practitioner, but a specific inquiry as to 
whether or not this or that preparation contains or does not 
contain the necessary or the undesirable ingredient, whether 
the thing is of the composition or of the strength represented, 
and a few minutes' work in the laboratory, especially if aided 
by the microscopical tests given in a subsequent chapter, will fre- 
quently be found sufficient to answer questions of this character. 

The tests made in the dry way are not as delicate, nor are 
the results obtained (especially negative ones) as conclusive, as 
those of a systematic analysis of the substance in solution, and 
in occasional cases it may be necessary to resort to the more 
tedious process. 

Before undertaking the analysis of a substance, note care- 
fully its physical properties of odor, color, and solubility; also 
whether it is magnetic, metallic, or crystalline. 



ANALYSIS IN THE DRY WAY 103 

The volatile acids, certain ammonium compounds, bromine, 
and iodine may be detected frequently by their odor. 

Colors or Salts and Solutions. 
The following colored salts are soluble in water: 

Black Silver albuminate (argyrol, etc.). 

Violet or purple Chromic salts and permanganates. 

Cr0 3 and acid chromates, KaFeCy6, sodium- 



nitro-prusside, H 2 PtCl6. 

Reddish brown or purple-red Manganic salts. 

Reddish yellow Ferric salts and AUCI3. 

„ „ f Neutral chromates of the alkalis, salts of 

Yellow < 

[ uranium. 

Pale yellow KjFeCye (Potassium ferrocyanide). 

Pink Salts of cobalt. 

Pale pink Manganous salts. 

~ f Ferrous salts, nickel salts, certain copper 

Green { salts. 

Dark green Some chromic salts. 

Blue-green Chromates. 

Blue Cupric salts. 



The following colored substances are insoluble in water: 

{Carbon and carbides, metals, many metallic 
sulphides, oxides of Cu, Fe, Mn, and Pb. 
Iodine is bluish black. 

Red HgO, HgS, Hgl 2 , Pb 3 4 , AS2S2. 

Brick-red Amorphous phosphorus, Fe 2 03. 

Light brown PbO (litharge). 

S, HgO, CdS, As2S 3 , Pbl 2 , Ag 3 P0 4) ammo- 
Yellow •! nium phosphomolybdate, and chromates 

of the heavy metals, PbCr0 4 , BaCr0 4 . 
Some copper compounds, Cu 2 I 2 , Paris green, 
etc.,Cr 2 3 . 

lpounds, Prussian blue, 
anhydrous salts of cobalt. 



Green 



w j Some copper com[ 

"\ ultramarine; anhy 



104 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

METHODS OF EXAMINATION. 

Powder the substance and apply tests described in this 
chapter, which will be considered in the following order: 

A. Ignition with free access of air. 

B . Closed- tube test. 

C. Flame test on platinum wire. 

D. Examination with the blow-pipe on plaster slab. 

E. Bead tests on platinum wire. 

F. Special tests, distinguishing or confirmatory. 



A. Ignition in Air. 

This test may be made on a crucible cover or on platinum 
foil. If there is any probability of I, Br, CI, P, or easily reduced 
metallic compounds in the unknown substance, the platinum 
foil is likely to be destroyed; hence, the porcelain is recommended. 

The heat employed should be very low at first; then it 
should be gradually increased and the test carefully watched. 

The majority of phenomena occurring under A are more 
easily observed in the test made with closed tube, B, and will 
be given under that head. 



Observed Phenomena. 
The substance melts and steam is given off. 



The substance burns (a) at comparatively low 
temperature with blue flame and odor of 
SO2 or burning matches. 

(b) With yellow flame and much smoke. 

(c) Blackens and then burns at fairly high 

temperature, leaving white or gray ash. 

(d) Blackens without burning. 

Vapors are given off: 

(a) Of a violet color. 

(b) Of a red-brown color. 

(c) Of a greenish-yellow color. 

(d) White, practically odorless. 



Indications. 

Water of crystallization. 
NH4NO3 or H2C2O4, which 
entirely disappears. 

Sulphur. 



Fat, waxes, resins, etc. 
Carbonaceous matter other 

than fats, etc. 
Formation of oxides of Fe, 

Co, Ni, or Cu. 

Iodine. 

Br or nitrogen oxides. 
Chlorine or C10 2 . 
Some ammonium salts, 
NH4CI, (NH 4 ) 2 S0 4 , etc. 



ANALYSIS IN THE DRY WAY 



i°5 



Observed Phenomena. 

(e) White with odor of NH 3 . 
(/) White with odor of garlic, 
(g) White and yellow with ammoniacal or 
empyreumatic odor. 
The substance decrepitates. 

Examine residue on foil (porcelain); add a drop 
or two of water and test with litmus-paper. 
If found to be acid. 
If alkaline without blackening. 

If alkaline with blackening. 



Add a drop of dilute HC1, effervescence. 



Indications 

Ammonium carbonate. 

Arsenic. 

Organic matter. 

Water held mechanically by 
crystals, as NaCl, etc. 



Acid salts. 

Fixed alkali hydrates or 
carbonates. 

Carbonate formed by com- 
bustion of organic com- 
pounds. 

Carbonates. 



B. Closed-tube Test. 

Select a tube of soft glass about five or six inches in length. 
Seal one end and enlarge slightly. Into the bulb thus formed 
introduce a few grains of the unknown powdered substance. 
Heat carefully, making the following tests at various stages of 
the process. Note the odor of escaping gases. 

Test for oxygen by inserting a glowing splinter into the tube. 

Test for combustible gases by occasionally applying flame 
to the open end of the tube. 

Bring to the mouth of the tube a clear drop of Ba(OH) 2 
solution. If the drop becomes turbid, C0 2 is indicated. 



Observed Phenomena. 

Steam condenses in cold part of tube. 
Oxygen is evolved. 



Carbon Dioxide is evolved. 



A Combustible Gas is formed: 

(a) Burning with a luminous flame, black 

residue remains in tube. 

(b) Burning with a blue flame. 

(c) Burning as in (b) and with odor of S0 2 . 

A Sublimate forms in the cooler part of the 
tube. Examine under microscope. 



Indications. 

See under A. 

A peroxide, chlorate, some 
oxides (as HgO), alkali 
nitrates. 

Carbonates, oxalates (at 
high temperature), or- 
ganic matter. 

Hydrocarbons from organic 

matter. 
CO from oxalates. 
H 2 S from moist sulphides. 



106 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 



Observed Phenomena. 

Colorless with partial decomposition. 

Color is white with production of garlic odor, 

crystalline. 
Color is white when cold. Yellow when hot, 

crystalline. 
Color is white — it sublimes directly without 

melting and blackens with NH 4 OH. 
A white sublimate which by treatment with 

slaked lime yields NH3. 
A white sublimate of AS2O3 with black residue 

in tube and odor of acetic acid. 
Sublimate is gray, consisting of small glob- 
ules which can be made to unite by rubbing. 
Sublimate consists of reddish yellow to red 

globules, yellow when cold. 
Sublimate darker than above and reddish yellow 

when cold. 
Sublimate is brown to black "metallic mirror," 

soluble in NaClO. 
Ditto; dead black, insoluble in NaClO. 
Sublimate is black accompanied by violet vapor. 

Sublimate black, turning red when rubbed. 
No sublimate is formed, but the color changes 
to 

Yellow when hot, white when cold. 

Reddish brown when hot, yellow when cold. 

Black when hot, red when cold. 

Black when hot, brick-red when cold 

Dark orange when hot, yellow when cold. 
Black residue without other visible mani- 
festation. 
Substance melts without a sublimate being 
formed. 



Indications. 

Oxalic acid. Plate I, Fig. 1. 
AsaOs. Plate I, Fig. 2. 

HgCl 2 . Plate I, Fig. 3. 

HgCl. 

Ammonium salts. Plate I, 

Fig. 4. 
Paris green. 

Hg from HgO, amalgam, 

etc. Plate I, Fig. 5. 
Sulphur. 

Native sulphide of arsenic. 

Metallic arsenic. 

Metallic antimony. 
Iodine. Plate I, Fig. 6. 
HgS, cinnabar. 



ZnO. 

PbO or Bi 2 3 . (See D.) 

HgO (Hg sublimes). 

Fe 2 3 . 

Chromates of Pb, etc. 

Oxides of Cu, Co, etc. (See 

A.) 
Salts of the alkaline metals. 



C. Flame Test with Platinum Wire. 



Introduce the substance on platinum wire into the edge of 
the flame. More satisfactory results are sometimes obtained 
if the solid is first moistened with HC1 (page 80, note). The 
flame is colored as follows: by Na, yellow; K, violet; Ni, car- 
mine; Sr, crimson; Ca, orange-red; Ba, yellowish green; Cu, 
usually bright green; CuCl 2 , an intense blue; H3BO3, pale green; 
Sb, greenish blue; Pb, As, Bi, livid blue. 



PLATE I. — SUBLIMATES. 




Fig. i. 
OxaKc Acid (Sublimed). 




Fig. 3. 
Mercuric Chloride (Sublimed). 





Fig. 2. 
Arsenic Trioxide. 




Fig. 4. 

Ammonium Sulphate (Sublimed). 




Fig. 



Mercury from HgO. 



Fig. 6. 
Iodine. 



ANALYSIS IN THE DRY WAY 107 

D. Blowpipe Test on Plaster* 

Smooth plaster slabs about one inch wide and four inches 
long are well suited for these tests. These may be prepared by 
making a magma of calcined plaster and pouring upon a glass 
plate. Before it hardens mark deeply with a spatula into slabs 
of desired shape and, after it is thoroughly dried, break as marked. 

Make a little depression near one end of the slab and in it 
place a small amount of the substance to be tested; then if 
a fine oxidizing flame is made to play over the surface of the 
assay, characteristic coatings of oxide or sublimate may be 
obtained. 

In many cases the character of the substance may be deter- 
mined more easily by first moistening the assay with various 
reagents. Tetrachloride of tin, cobalt nitrate, and " sulphur 
iodide " are the most valuable of the reagents so used. The 
" sulphur iodide " is not of definite composition, but a mixture 
of about equal weights of sulphur and potassium iodide. 

D. I. Examination without Reagents. 



Observed Phenomena. 

Substance melts to bright metallic globules 
with brownish-yellow deposit near assay. 

Requires high heat. Assay revolves. 

Substance melts to bright globule with coat- 
ing on plaster, deep orange when hot, light 
yellow when cold. 

Substance remains or becomes black without 
melting. No coating on plaster. 

Substance volatilizes with white fumes, but leaves 
dark stain; gray to black. 

Substance melts with white or gray oxide on 
assay. 

Forms a white or gray oxide without fusion. 
Coating on plaster is yellow over brownish 
black. 



Indications. 
Silver. 



Lead or bismuth. (See D. 
II.) 

Copper or iron. (See A; 

also F.) 
Antimony or arsenic. (See 

F.) 
Tin. (See D. III.) 

Cadmium. 



* Substances sufficiently identified by previous tests have been omitted. This 
method will be found useful mainly in the identification of metals. 

The author was greatly aided in the preparation of this list by Mr. Geo. F. S. 
Pearce of the Harvard Dental School, who carefully verified each test. 



ioS SALTS OF THE METALS AND QUALITATIVE ANALYSIS 



Observed Phenomena. 

Forms bulky white oxide with active combus- 
tion of assay. 
Forms gray coating easily volatilized. 

Cherry-red — crimson to black according to 
amount of substance deposited. Odor of 
rotten horse-radish; coating not permanent. 

White coating or white fumes at very high heat. 
Assay burns with bluish-white light. 

Silver- white. Assay remains unchanged. 



Indications. 
Magnesium. 

Mercury from amalgams. 

(See D. II.) 
Selenium. 

Zinc. (See D. III.) 
Platinum, metallic. 



D. II. Cover Substance with KI and S. Use Oxidizing Flame. 



Observed Phenomena. 

Dirty-white and light-gray coating. Treated 
with fumes of strong NH 3 and again placed 
in oxidizing flame gives bright-red color. 
Metallic globule is dull and brittle. 

Dirty white half an inch from assay. Brown 
directly under assay. No change when treated 
as above with strong ammonia fumes. Metallic 
globule is bright and malleable. 

No coating near assay. Lead-colored, one to 
one and a half inches, shading to yellow. 

Coating bright red when hot, fading to yellow 
when cold. 

Fine brown coating, very volatile. 



Indications. 



Bismuth. 

Lead. 

Mercury. 

Cadmium. 

Antimony. 



D. III. Examination with Solution of Cobalt Nitrate. 

Heat substance on plaster in the oxidizing flame, moisten 
well with cobalt nitrate, and again apply oxidizing flame. 



Observed Phenomena. 

Color is deep blue. 

Substance is infusible. 

Color is fine blue. Substance fusible. 

Color is yellowish green. 
Drab to bluish green. 



Indications. 

Aluminium. 

Infusible silicates. (See F.) 

Alkaline silicate, borate, or 

phosphate. 
Zinc. 
Tin. 



D. IV. Examination with Tetrachloride of Tin. 
Observed Phenomena. Indications. 



Coating pale blue to lavender. 
Coating fine blue, in places almost black. 
Delicate pink to red produced only by oxidizing 
flame. 



Bismuth. 

Antimony. 

Neutral and acid chromates. 



ANALYSIS IN THE DRY WAY 109 

E. Bead Tests. 

The bead tests are made with borax, as described on page 61 , 
or in a similar manner with microcosmic salt, NaNH 4 HP0 4 , 
which by action of the heat gives up NH 3 and H 2 0, becoming 
sodium metaphosphate, NaP0 3 . These substances fused on a 
loop of platinum wire unite with many of the metallic oxides, 
forming " beads " of various characteristic colors, some of the 
more important being given below. 

With Borax. 

Co in the oxidizing flame gives an intense blue bead. 

Ni gives a red-brown, yellow when cold. 

Cu gives a green, blue, or bluish green when cold. 

Cr gives green. 

Fe gives a red, yellowish when cold. 

Mn gives an amethyst. 

With Microcosmic Salt. 

Cobalt, copper, nickel, and iron give colors similar to those 
obtained with borax. Manganese gives a violet bead when 
heated in the oxidizing flame, but a colorless one in the reducing 
flame. 

F. Special Tests Distinctive or Confirmatory 

The oxides of copper and iron may be distinguished by adding 
a drop of HN0 3 , warming gently to drive off excess of acid 
(high heat will decompose the nitrate, giving the oxide again), 
and then adding a drop of solution of K 4 FeCy 6 . Fe will give 
a dark-blue coloration; Cu will give a brown. 

To distinguish between As and Sb stains, add a drop of hy- 
pochlorite solution (NaCIO). The arsenic stain will dissolve; 
the antimony stain will remain unaffected (see page 36). 



HO SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Antimony gives a very characteristic coating on plaster if 
treated with tetrachloride of tin. The coating is bluish black 
near assay, fading away to a very delicate color at greater 
distance. It appears almost immediately and is permanent. 

In case of suspected silicates make the " silica skeleton " with 
a bead of microcosmic salt (page 98). 



PART II. 
DENTAL METALLURGY. 

INCLUDING THE CHEMISTRY OF ALLOYS, AMALGAMS, 
SOLDERS, AND CEMENTS. 

CHAPTER XI. 

THE METALS. 

Properties of the Metals. 

Metals are malleable in order as follows from gold, the most 
malleable, to nickel, the least: Au, Ag, Al, Cu, Sn, Pt, Pb, Cd, 
Zn, Fe, Ni. 

Metals are tough or tenacious in order as follows: Fe, Cu, 
Pt, Ag, Au, Al, Zn, Pb. 

The ductility of metals ranges from greatest to least as 
follows: Au, Ag, Pt, Fe, Ni, Cu, Cd, Al, Zn, Sn, Pb. 

Metals conduct heat and electricity in the same order until 
tin is reached. From tin the order given is correct for heat 
but not for electricity: Ag, Cu, Au, Al, Zn, Cd, Sn, Fe, Pb, 
Pt, Bi. 

The melting-point of the various metals is of considerable 
importance in the preparation of alloys. The following table 
has been compiled from the latest available results. The de- 
grees given are according to the centigrade scale : 

Ir 2200 Al 657 

Pt 1780 Mg 500 (burns) 

Ni 1450° Sb 632 

Cast steel 1300 Zn 418 (burns) 

Cast iron 1200 Pb 327 

Cu 1084 Cd 322 

Au 1075° Bi 268 

Ag 962 Sn 232 



112 DENTAL METALLURGY 

If lead, which is the softest of the common metals is taken 
as a standard and considered as one, the other common metals 
are harder in the proportion shown in the following table taken 
from Hall's Dental Chemistry. 



Pb i 

Sn i 

Cd i 

Al i 

Bi i 

Au ". i 

Ag i 



o Sb 1.8 

2 Zn 1.9 

4 Pt 2.0 

5 Cu 2.4 

6 Fe 2.4 

7 Ni 2.5 



The expansion of the various metals under the influence of 
heat is fairly constant and there have been determined co- 
efficients of expansion. These represent the amount of linear 
expansion of the metals due to a rise in temperature of i° C, 
usually from o° to i°. The coefficients are not absolutely con- 
stant, and the amount of expansion observed between o° and i° 
may differ somewhat from that between 50 and 51 . The 
coefficients vary widely for the different metals; for instance, 
in passing from o° to ioo° mercury expands 1/16 of its linear 
measure, copper 1/598, and platinum 1/1123. 

Hall's Dental Chemistry gives the following table of expan- 
sion from cadmium to platinum (o° — ioo°) : 

Cd 1/326 Ag 1/518 Ni 1/787 

Pb 1/342 Cu 1/598 Fe (cast) 1/934 

Zn 1/343 B i !/ 6l 7 Sb 1/952 

Al 1/432 Au 1/689 Pt 1/1123 

Sn 1/448 

According to the kinetic-molecular theory every metal has 
a certain tendency to pass into solution when immersed in a 
fluid. If the fluid contains the ions of some other metal of less 
relative electromotive force the ions in solution will deposit 
upon the metal, while the metal-ion passes into solution; i.e., 
the one metal is precipitated by the other. In the list Au, Pt, Ag, 
Hg, Bi, Cu (Pb, Sn), Co, Cd, each metal precipitates all pre- 



THE METALS 



"3 



ceding it (lead and tin are too nearly alike for either to com- 
pletely precipitate the other) and is precipitated by all which 
follow. All in the list are precipitated by Zn, Mg, Al, K, and Na. 
Iron precipitates copper and the preceding metals but it is 
only partly precipitated by those which follow. 

The metals are electropositive in the following order from 
zinc, the most positive, to gold, the least: Zn, Cd, Fe, Ni, Sn, 
Pb, Cu, Bi, Sb, Hg, Ag, Pt, Au; and carbon is negative to all. 
It will be noticed that this list of metals is the same, but in 
reversed order, and is arranged for the same reason as the list 
given in the paragraph above. 

Thus if a battery is constructed with zinc as represented in 
the cut (Fig. 7), and iron in place of the carbon, then the iron will 
be electronegative to the zinc, and hydrogen will be evolved 
from its surface; if, on the other hand, iron is 
used in place of the zinc, and the carbon remains z, 
as in the cut, the iron will be electropositive to 
the carbon, and oxygen will be evolved from its 
surface. This property of metals has a direct 
bearing upon dental science, because human saliva 
may be an exciting fluid for the generation of gal- 
vanic currents, its activity being increased by an 
abnormal reaction either acid or strongly alkaline, 
and it is only necessary to place in the mouth 
properly related metals, as amalgam fillings or otherwise, to pro- 
duce the elements of a galvanic battery. 

The currents thus generated are, of course, infinitesimal, but 
they are constant and may aid in the disintegration of fillings 
and in the solution of the constituent metals. Regarding the 
extent to which electric currents may exist in the mouth, see 
Miller's Micro-organisms of the Human Mouth. 




Fig. 7. 



CHAPTER XII. 
ALLOYS. 

An intimate union of two or more metals, usually produced 
by fusion, forms an alloy. Such a union of one or more metals 
with mercury is an amalgam. 

An alloy designed to be used in the preparation of dental 
amalgams is known as an amalgam alloy. 

Some metals can be fused together in all proportions, as 
lead and silver. Others can be made to unite only in limited 
proportions, as lead and zinc. Lead will carry only 1.6% of zinc, 
while zinc will unite with only 1.2% of lead. Excess in either 
case separates out. 

The properties of an alloy are, as a rule, the modified proper- 
ties of its constituent metals. An exception to this rule might 
be made of the sonorous quality of bell-metal and like alloys, 
this being hardly a property of the constituent metals at all. 

Following are some of the more common alloys. The pro- 
portions given are general formulae and may, as a rule, be varied 
considerably: 

Aich's metal,* Cu 60%, Zn 38.2%, Fe 1.8%. 

Aluminium bronze, yellow, resembles gold, Cu 92, Al 8. 

Bell-metal, Cu 80, Sn 20. 

Brass, Zn 1 part, Cu 2 parts. 

Britannia metal, Cu 2, Sn 82, Sb 16. 

Bronze, Cu 65 to 84, Zn from 31.5 to n, Sn from 2.5 to 4. 

Coin silver, Ag 90, Cu 10. 

Dental alloys, see page 125. 

Dental gold, Cu 85, Zn 15. 

* Hepburn. 
114 



ALLOYS 115 

Dutch metal, Cu 84.5%, Zn 15.5%. 

German silver,* Cu 50, Ni 30, Zn 20. 

Gun metal, Sn 11, Cu 100. 

Mannheim gold, Cu 75%, Zn 25%. 

Mosaic gold, Cu 50%, Zn 50%. 

Solder, see page 129. 

Sterling silver must contain 92.5% Ag. 

Type metal, Pb 78, Sb 15, Bi 7. 

For fusible metals (Mellot's, Wood's, Rose's, etc.) see page 1 28. 

All alloys (excluding amalgams) are solid at ordinary tem- 
peratures with one exception; this one is an alloy of one part 
potassium with three parts sodium. 

The melting-point of an alloy is often lower than that of the 
metals entering into its composition and usually lower than the 
mean melting-point of its constituents. 

In making alloys the tendency to separation of the several 
metals is greater if the alloy is allowed to cool slowly; hence 
three essentials in the process are: Complete fusion, which 
makes possible thorough mixing, and after this has been attained 
rapid cooling. As the fused mass is to be cooled as quickly 
as possible after fusion is complete, it is desirable to use the least 
amount of heat practicable in effecting the desired result. To 
this end fuse first the metal with the lowest melting-point, 
then add other metals in the order of their melting-points. 
The more difficultly fusible metal will in a sense dissolve in 
the more easily fusible metal; an alloy is formed and its tem- 
perature has been kept far below the melting-point of the high 
fusing constituent. This general rule, however, may be modified 
by the proportion of metal used; thus, in making a silver- tin 
amalgam-alloy containing 60% of silver it is better first to melt 
the silver under a flux of carbonate of sodium or borax to prevent 
superficial oxidation, then add the tin, and lastly any other 

* Composition of different samples of German silver may differ widely; some 
contain about 2.5% of iron and the amount of copper may vary from 40 to 60%. 




Il6 DENTAL METALLURGY 

metal to be used. The mixing is attained by stirring with a 
wooden stick and the cooling by turning quickly into a cold clean 
mold. For class work or in making small amounts (twenty 
grams) of alloy, the Fletcher melting arrangement shown in 
Fig. 8 is very convenient. The metals are melted 
in the graphite crucible and then by tipping up the 
whole contrivance the melted metals flow back into 
the ingot mold. If the alloy is to be used in the 
preparation of dental amalgams it must be re- 
duced to fine turnings or filings suitable for ready 
amalgamation. This is best accomplished in the 
laboratory by means of a coarse file, the ingot being held by a 
vise. The fine particles of iron must next be carefully removed 
with a magnet, and then the filings may be annealed if desired. 
The annealing of the amalgam-alloys may be accomplished 
by placing the freshly cut sample in a dry test-tube and keeping 
the test-tube in boiling water for ten or twelve minutes. It has 
been claimed that this process is one of superficial oxidation and 
the changes produced seem to be consistent with this theory. 
Again, it is claimed that the change is a molecular one of some 
sort due to change of temperature, and Prof. G. V. Black has 
shown that an alloy will anneal as rapidly in an atmosphere of 
nitrogen as of oxygen. The modification of properties produced 
by annealing varies somewhat with the composition of the alloy; 
for instance, the liability to discoloration is less in the annealed 
than in the unannealed sample, if the alloy contains silver and tin, 
or silver, tin, and zinc, but if copper is a constituent the reverse 
condition has been found to exist. 

It has been shown that the freshly cut amalgam alloys 
require more mercury for amalgamation than the annealed 
alloy. The annealed alloy also is slower in setting and contains 
a smaller proportion of impurities (metallic oxides) which de- 
tract from the strength of the amalgam. 

Professor Black has shown that while it may be possible to 



ALLOYS 117 

stop the process of annealing at such a point that a given alloy 
will neither shrink nor expand, it is easy to carry the process 
too far and the farther it is allowed to go the greater the shrink- 
age. It is probably true that the exact effect of annealing 
will vary with the composition of the alloy, and with different 
proportions of metals in alloys of the same general composition. 

In annealing platinum a high degree of heat is required, but 
the heat should be raised gradually, and in this case, as with 
gold, the electric furnace furnishes an ideal method. 

Eutectic Alloys. — The term eutectic signifies lowest melting- 
point or freezing-point, and is perhaps best illustrated by water 
and salt. 

If a salt solution, so made that it contains 23.6% by weight 
of sodium chloride, is cooled to a temperature of — 22 C, the 
two substances crystallize together in the form of a very intimate 
mechanical mixture of ice and salt crystals. This is known as 
a eutectic mixture and these proportions, the eutectic ratio 
for salt and water. 

Upon lowering the temperature of a solution which contains 
less than 23.6% of salt the excess of water crystallizes in a com- 
paratively pure form, leaving a brine of constantly increasing 
degree of concentration until the eutectic proportions are reached. 
If the salt solution were stronger than 23.6% the salt would crys- 
tallize out leaving a brine of decreasing concentration. Both 
of these latter crystallizations however would take place above 
— 22 C, so the point where the eutectic mixture crystallizes 
is the lowest possible for a mixture of this particular nature. 

In exactly this way a eutectic alloy is one which has the 
lowest possible melting-point obtainable by use of the given 
constituents; and in similar manner also, when an excess of one 
or the other metals is used, we may regard the mixture as a 
solution of the eutectic alloy in an excess of metal. 

The physical differences between the eutectic alloy and " the 
solid solution " may be shown by microscopical examination, 



Il8 DENTAL METALLURGY 

the eutectic mixture being much more intimate in character 
than the other. This examination is made by reflected light upon 
a surface polished as perfectly as possible. The method of pro- 
cedure is as follows: a thin piece of alloy is polished by the use 
of emery disks and paper of varying grades until the surface 
is as smooth as possible, then the polishing is completed by the 
use of the very finest paper, then by a rapidly rotating wheel 
covered with cloth upon which jeweler's rouge has been rubbed. 
The most satisfactory results are obtained if the surface of the 
alloy is kept wet. 

The specimen may be mounted in soft wax contained in a 
brass ring with perfectly parallel edges, as it is essential that the 
polished surface be parallel to the microscope stage. After 
the examination of the polished surface it may be etched by 
various chemicals such as nitric and hydrochloric acid and again 
examined. 



CHAPTER XIII. 
AMALGAMS. 

In general, amalgams may be made in three different ways: 
First, by direct union of the constituents, as in the manufacture 
of sodium amalgam (page 121); second, by electrolysis of 
strong solutions of metallic salts in presence of mercury, as 
in copper amalgam (page 122), and third, by double decompo- 
sition as illustrated in the preparation of ammonium amalgam 
(page 121). 

The nature of the amalgam seems to vary with the compo- 
sition; that is, some amalgams are apparently true chemical 
compounds, others are solutions of one metal in another, or in 
mercury, while still others are mixtures of these two, or solutions 
of the compound; for example silver, gold, and copper will form 
definite compounds with mercury from which the mercury cannot 
be separated by heat even at a temperature of 450 C, — nearly 
a hundred degrees in excess of the boiling-point of mercury, — 
but these compounds readily unite with larger proportions of 
mercury in the formation of amalgams. Also platinum, tin, 
cadmium, and bismuth do not retain mercury at 450 C; and 
potassium and sodium form definite crystalline compounds with 
mercury. 

Amalgams possess the peculiar property of " setting " or 
hardening within a short time after mixing. This in some cases 
seems to be a process of crystallization, and in all cases is 
probably due to molecular rearrangement of some sort. 

After an amalgam has " set " to a sufficient extent to make 
it hard to work it may be softened by application of gentle 
heat. Continued reheating is detrimental to the quality of the 

119 



120 



DENTAL METALLURGY 



amalgam, and should be avoided; this is particularly true of 
copper amalgam. It is also possible to sometimes restore the 
plastic quality of an amalgam by adding a further slight amount 
of mercury, but the union of the second lot of mercury after the 
first has partly hardened is very unsatisfactory and results in a 
weakened product. 

Flow of Amalgams. — This property may be defined as the 
tendency to flatten or change shape under stress or pressure. 
It is common to most amalgams (copper amalgam being an 




Fig. 9. 



exception, according to Dr. Black), and is possessed by many 
alloys other than amalgams. 

Tests for " flow " may be made with the " dynamometer " 
on cubes of alloy or amalgam measuring one-tenth of an inch each 
way and the results expressed in percentage of increase or de- 
crease of one dimension. The dynamometer used for this pur- 
pose is pictured in Fig. 9 and is a modification of the apparatus 
devised by Dr. Black and described on pages 408 and 409 of the 
Dental Cosmos, Vol. 37, A- A being the molds in which the 
cubes of amalgams are set and B the point in the apparatus 
where the cube after setting is introduced with a pair of fine 
forceps. The dial is supplied with two hands, one which flies 



AMALGAMS 121 

back the instant the cube breaks, the other remaining to indicate 
the number of pounds applied necessary to crush the cube. 
The cubes of i/io inch are best suited for students' practice, 
with a dial constructed to record 250 pounds pressure. For 
accurate comparisons of thoroughly made amalgams the cubes 
must be made smaller. 

Binary amalgams, as they are sometimes called, are those 
consisting of only one metal besides mercury. These are rarely 
used in dental practice, but from them the properties of the 
amalgamated metal are most easily observed. 

Sodium amalgam may be made by direct union of the con- 
stituent elements. The mercury should be placed in an open 
dish under a hood, and the sodium added in small well-cleaned 
pieces. 

The union is accompanied by a slight hissing noise, an eleva- 
tion of temperature and evolution of vapor carrying more or 
less mercury, hence dangerous to breathe. An amalgam con- 
taining 1% sodium is a viscid liquid; if it contains 5% sodium 
it is a hard solid and intermediate percentages give varying 
degrees of firmness. Sodium amalgam, if made with arsenic-free 
mercury, is a very convenient reagent to use in making 
Fleitmann's Test (page 35). 

Aluminium amalgam is easily made with aluminium filings and 
mercury or dilute solution of mercuric chloride. This amalgam 
decomposes water at ordinary temperatures, giving free hydrogen 
and aluminium hydroxide. 

Ammonium amalgam has no use in dentistry, but it is of 
interest in that it is the nearest approach which we may attain 
to the isolation of the purely hypothetical metal ammonium. 
It is easily made by adding sodium amalgam to a cold saturated 
solution of ammonium chloride, thus illustrating the third 
general method of preparation of amalgams. It rapidly decom- 
poses at ordinary temperature with the liberation of free hydro- 
gen ammonia-gas and metallic mercury. The hydrogen thus 



122 DENTAL METALLURGY' 

liberated exhibits the properties of nascent hydrogen, indicating 
that in the amalgam it existed in true chemical combination, that 
is NH4, rather than in any physical solution. At ordinary tem- 
perature ammonium amalgam is a soft, pasty, very porous 
mass, but at much reduced temperature it becomes solid and 
crystalline, although at — 39 (the freezing-point of mercury) 
hydrogen and NH3 are still given off. 

Copper amalgam is by far the most valuable of this class 
of amalgams. It may be made by amalgamating precipitated 
copper after moistening it with nitrate of mercury (Essig). 
The precipitated copper may be prepared by action of metallic 
zinc in a slightly acid copper sulphate solution, but must be 
thoroughly washed with hot water to free it from zinc chloride. 
The amalgamation may be effected by use of mortar and pestle. 
Rollins' method * by electrolysis of strong copper sulphate solu- 
tion is rather unwieldly, but illustrates very well the second 
general process for the manufacture of amalgams. 

Copper amalgam, according to Black, is absolutely rigid 
after it has once set and does not flow even to a slight extent. 
It is fine-grained and very hard. It is reduced in strength by 
reheating and does not expand or contract. In the mouth copper 
amalgam dissolves with comparative rapidity owing to the 
ready formation first of copper sulphide, then, by the oxidation of 
this compound, of the sulphate. It blackens rapidly and in 
consequence of the tendency just mentioned, to dissolve, it may 
penetrate the dentine and thus discolor the tooth itself. 

Gold amalgam is readily made, but does not, by itself, harden 
well. An amalgam containing one part of gold to six of mercury 
will crystallize in four-sided prisms (Litch). 

Magnesium amalgam may be easily produced, but like 
the amalgams with aluminium or sodium it decomposes water 
with the evolution of hydrogen. 

* Details of this method may be found in the Boston Medical and Surgical 
Journal, February, 1886; also in Mitchell's Dental Chemistry. 



AMALGAMS 123 

Platinum amalgam is very smooth, is formed with difficulty 
unless the platinum is very finely divided, and, like gold, does not. 
harden well. 

Silver amalgam, easily made but tends to expand. 

Tin amalgam, alone, shrinks badly. 

Zinc amalgam, readily made, is white, but too brittle to be of 
service. 

Cadmium amalgam may be easily made at ordinary tem- 
perature, " sets quickly, and resists sufficiently, but fillings con- 
taining it gradually soften and disintegrate and may stain 
the dentine bright yellow by formation of cadmium sulphide. " 
(Mitchell.) 

Effect of Various Metals in Amalgam Alloys. 

With the properties of these simpler combinations before 
us it becomes easy to understand the effect the addition of the 
various metals will have upon the properties of a silver- tin 
alloy; for practically all amalgam alloys are silver- tin alloys, 
either simple or combined with one or more other metals. 

Silver and tin are the most valuable constituents of amalgam 
alloys. Silver is essential to the proper setting and hardening 
of the amalgam. It tends to increase expansion and to hasten 
setting, while tin possesses the opposite characteristics. Com- 
bined with tin in the proportion of 65% silver to 35% tin, it 
forms an amalgam alloy perhaps more largely used than any 
other. It was this combination that Dr. Black succeeded in 
" annealing to zero," that is, so that upon testing it showed 
neither expansion nor contraction. 

Pure silver- tin alloys will flow from 2.5 to 10%. 

Dr. C. M. McCauley in an article on amalgams published 
in the Dental Cosmos for February, 191 2, states that the formula 
of 65% silver and 35% tin will produce an amalgam which gives 
no shrinkage if the freshly cut alloy is used, but upon annealing 
the alloy it was necessary to use about 74% silver. He further 



124 DENTAL METALLURGY 

states that 5% of copper for an equivalent of silver increases 
the strength of amalgams made from silver-tin alloys. 

Dr. McCauley also tells us that a contraction of one ten- 
thousandth of an inch will admit organisms producing caries 
into a tooth cavity, but that the expansion of the finished filling 
of about one twenty-thousandth of an inch is a desirable result. 

The larger the proportion of tin the easier will the alloy 
cut, but the coarser will be the filings. 

Zinc added to a silver-tin alloy tends to whiten the amalgam, 
hastens setting, increases the flow, and, according to Essig, 
" causes a great but slow expansion." 

Dr. McCauley, quoted above, states that zinc is unfavor- 
able in its action on other metals in a dental alloy and detrimental 
when used to the extent of only one per cent, because of its 
tendency to produce a constant expansion for several months, 
even though tests made during the first few days were satis- 
factory. 

Cadmium, see page 123. 

Antimony gives a fine grain alloy and when the silver is less 
than 50% is supposed to control shrinkage. 

Bismuth will increase the flow of the amalgam; it is some- 
times used in low-grade silver-tin alloys to control shrinkage. 

Copper tends to diminish flow and gives a strength under 
pressure, sets quickly, gives better margins, and by some is 
believed to have preservative influence on the tooth substance, 
but the more copper in an alloy the more rapidly does it dis- 
color. 

Gold. — From three to seven per cent, of gold in a silver-tin 
alloy diminishes shrinkage, helps the color and adds to crush- 
ing strength. The filing from such an alloy will be very fine. 

Dr. Black says 5% of gold gives a softer working property 
but retards setting of the amalgam, and makes it otherwise 
difficult to give a good finish to the filling (Dental Cosmos, 
Vol. 38, page 988). 



AMALGAMS 



125 



Platinum according to Black, is not a desirable addition 
to a silver-tin alloy. It gives an alloy furnishing very fine filing, 
which produces a dirty working, slow-setting amalgam. 

Excess of Mercury. — In the preparation of an amalgam 
from a dental alloy it is usual to add more mercury than the 
finished product requires and then squeeze out the excess be- 
tween the ringers or otherwise. In filling a cavity, still more 
mercury is forced out, so that the composition of the deeper 
portions of a filling varies from the outer portions and probably 
accounts for the inequalities in expansion or contraction. The 
excess of mercury from the surface of a filling may be absorbed by 
a little hot gold or pure tin or by finely-divided silver. 

Following is a short list of dental alloys, most of which may 
be easily prepared: 



Sn 



Au Cu 



Zn Sb 



Arington's (S. S. White's) 

*(C. A. S.) alloy, C. Ash Sons Co. 

Chase copper-amalgam alloy . 

Chase's incisor alloy 

*Fellowship alloy 

Flagg's submarine alloy 

Fletcher's gold alloy (old) 

High-grade alloy (7!% gold) 

Harris's amalgam alloy 

King's occidental alloy 

*Odontographic alloy 

*Standard alloy 

Standard dental alloy (Eckfeldt) 

60% silver alloy 

Temporary alloy 

*True dentalloy 

Twentieth century 



57-5 
27.16 

50 
40 
26.80 

35 
56 

4i.5 
48.1 

54-75 
26.48 

35-Q3 

40.6 

40 

88 

27.13 

27.13 



42.5 

66.54 

50 

50 

67-45 

60 

40 

49 
40 

42.75 

66.87 

53-55 

52 

60 

10 

65-9i 
67.03 



4 
7-5 



0.28 
8.82 
4-4 



5.02 
10 

5-73 
5 



4-9 

6.21 
2.76 
3 



5.21 
4.87 



0.90 



o-55 



2 
7 

2-5 

trace 



2 
1.52 



* Analyses by Dr. P. J. Burns of the Mass. Inst. Technology, reported in 
the Journal of the Allied Societies, June, 1908. 

These formulae have been selected from various sources with 
a view to giving the student opportunity to study effects ob- 
tained by varying percentages of tin and silver, and by introduc- 
tion of other metals, copper, zinc, etc. 



126 DENTAL METALLURGY 

The excess of mercury which has to be squeezed out of an 
amalgam carries with it more or less of the constituent metals. 
Hall found that whatever the amount of mercury expressed, it 
carried just about i% of tin. In the author's experience this 
amount has reached nearly i\% of tin. Silver is carried out to 
a much less extent than tin, so it is not impossible to carelessly 
make an amalgam and squeeze out enough mercury to change 
the proportion of silver and tin in the alloy. This change will, 
of course, be very slight, but we have seen that the contraction 
and expansion of amalgams may be affected by slight changes in 
composition. 

Tests for Amalgams. 

Color Test. — This is made upon a freshly amalgamated 
alloy, rolled into about the shape and size of a small pea, with 
a view to determine the amount of discoloration the amalgam 
is liable to undergo in the mouth. 

A ball of amalgam carefully smoothed on at least one side 
is placed for forty-eight hours in a saturated solution of hydro- 
gen sulphide, and after that time its color is compared with other 
amalgams similarly treated, or with amalgam of a similar com- 
position which has not been treated. 

Test for Expansion or Contraction. 

Black has shown that tests of this nature to be of any value 
must be made in such a way that the amount of change in the 
volume can be measured, and that the simple method of pack- 
ing glass tubes and using colored ink is wholly unreliable. 

The author uses for this purpose an apparatus similar to 
one described by Prof. Vernon J. Hall. The amalgam is packed 
closely into a " well " in a steel block, then the block is placed 
in the apparatus so that a counterpoised steel plunger rests on 
the column of amalgam. This plunger is operated by a very 
long needle and attached at a point so near the pivotal support 



AMALGAMS 



127 



of the needle that a rise or fall of the plunger of 1/2500 of an 
inch moves the tip of the needle, at the scale, 1/16 of an inch, 
or one degree. If the needle rises half a degree, which may 
easily be read, it would indicate an expansion of the amalgam 
of 1/5000 of an inch. 

There are two wells in each block and both of exactly the 
same depth. The figure given below will make this explanation 
easily understood, A being the steel block carrying the amalgam. 




Fig. 10. 

Test for Crushing Strength and Flow. — The test is made 
with Dr. Black's dynamometer (page 120) upon cubical blocks 
of amalgam which have been allowed to " set " for at least two 
days, and which measure 1/10 of an inch each way. 

Specific gravity may be obtained by weighing the sample 
first in water, then in air, and dividing the weight in air by the 
difference between the two weights obtained. 

It is instructive to make these tests on amalgam from alloys 
of varying composition, also on annealed and unannealed alloys 
of the same composition. 



CHAPTER XIV. 
FUSIBLE METALS AND SOLDERS. 

Fusible Metals. 

Under the head of fusible alloys properly come many of 
the alloys considered on page 129 as solders. The fusible alloy 
usually contains lead or bismuth together with tin and occasion- 
ally cadmium. This may be mixed in such proportions that 
the melting-point may be anything desired down to 63 ° C. 
These alloys are largely used in the dental laboratory. Mellot's 
metal, composed of bismuth eight parts, tin five parts, and lead 
three parts, is perhaps the most serviceable. This melts at about 
the temperature of boiling water. Wood's metal, melting at 
about 65 C, is composed of bismuth four parts, tin one, lead 
two and cadmium one. Rose's metal is bismuth two parts, 
tin one, and lead one. This melts at about 95 C. 

Babbitt Metal, much used in the manufacture of dies, is 
composed of copper one part, antimony two, and tin eight. The 
formula of common Babbitt metal on the market will be found 
to differ somewhat from the above and is not so well suited for 
dental purposes. 

According to Essig's Dental Metallurgy, Dr. C. M. Rich- 
mond used a fusible alloy in crown and bridge work which he 
states is as hard as zinc and can be melted at 150 F. and poured 
into a plaster impression without generating steam. The for- 
mula of this alloy is as follows: Tin twenty parts, lead nineteen, 
cadmium thirteen, and bismuth forty-eight. The following 
fusible-metal alloys are also suitable for the purpose. 

Tin. Lead. Bismuth. Melting-point of Alloy. 

122 236 F. or 113 C. 

5 3 3 2 ° 2 ° F - or 94° C. 

3 5 8 iQ7°F. or 92 C. 

128 



FUSIBLE METALS AND SOLDERS 



129 



The fusing-point of an alloy may be determined by melting 
under a liquid of sufficiently high boiling-point and then care- 
fully noting the temperature at which the melted alloy solidifies. 

Approximate results may be obtained by watching care- 
fully the melting of a very thin strip of alloy. 

Care must be taken that the temperature of the alloy is 
exactly the same as recorded by the thermometer. To insure this 
in the case of an alloy with low 
melting-point, it is usually sufficient 
to place the alloy in water or brine 
in a test-tube which is immersed in 
a beaker of similar fluid, then, by 
raising the heat gradually with con- 
stant stirring and by taking the 
mean of two or three determina- 
tions, fairly accurate results are 
obtained. 

Solders. 

Solders are alloys used in join- 
ing pieces of metal of the same or 
of different kinds. One of the con- 
stituent metals of the alloy forming 
the solder is usually the same as 
the surface upon which it is to be 
used, hence the various metals re- 
quire solders of special composition; for instance, common sol- 
der is entirely unsuited for soldering aluminium or gold. 

Common Solder is composed of tin and lead in different 
proportions. The larger the proportion of tin the finer is the 
solder, and the following three grades may usually be obtained: 
" Fine " or "hard " (tin two parts and lead one), " Common " or 
" medium " (tin and lead equal parts), " Coarse " or " soft " 
(tin one part and lead two parts) . 




— Apparatus for Taking 
Melting-Point. 



130 DENTAL METALLURGY 

In soldering metals, it is absolutely essential that the sur- 
faces be kept clean and free from superficial coating of oxides 
which may form easily with the elevated temperature employed 
in the process. Soldering acid and the various fluxes serve this 
purpose. Soldering acid is an acid solution of zinc chloride 
usually made by taking a few ounces of strong hydrochloric 
acid and adding zinc as long as the metal dissolves. Among 
the substances which may be used as a flux to prevent oxidation, 
rosin and borax are the most common. 

Soft Solders are those fusing below a red heat and include 
the common solders above mentioned, also the most fusible 
solders containing bismuth. These last are more properly 
fusible metals and are discussed under that head. 

Solders for Aluminium. — Aluminium solders with consider- 
able difficulty owing in part to the low melting-point of the 
metal, also to the fact that aluminium is attacked by alkalis, 
including borax, which makes it necessary to find some sub- 
stitute for this convenient flux. Essig recommends a flux con- 
sisting of three parts of copaiba balsam, one part of Venetian 
turpentine, and a few drops of lemon-juice. The mixture is to 
be used in the same manner as soldering acid with a solder con- 
sisting of zinc from eighty to ninety-two parts, aluminium from 
eight to twenty parts. Fused and finely powdered silver chlo- 
ride may also be used as a flux, the salt being reduced and the 
silver forming a superficial alloy. Richards recommends a 
solder for aluminium consisting of tin twenty-nine parts, zinc 
eleven parts, aluminium one part, phosphor- tin one part. 

Hall says that a solder which he has found very satisfactory 
may be prepared from aluminium forty-five parts, tin forty-five, 
mercury ten; further, that the following formulae suggested by 
Schlosser are particularly adapted to soldering dental work 
since they resist the reaction of corrosive substances. 



FUSIBLE METALS AND SOLDERS 



131 



Platinum-Aluminium 
Solder. 

Gold 3 . parts 

Platinum o . 1 part 

Silver 2 parts 

Aluminium 10 " 



Gold-Aluminium 
Solder. 

Gold 5 parts 

Copper 1 part 

Silver 1 " 

Aluminium 2 parts 



For soldering articles of aluminium the following solder is 
given in the Pharmaceutical Era, January 10, 1895: Silver two, 
nickel five, aluminium nine, tin thirty-four, and zinc fifty parts, 
to be used without flux. See also Dental Cosmos for 1906 (page 

us)- 

Solder for Brass requires a high heat for fusion and on this 
account is known as hard solder. 

Edwinson gives the following formulae: (1) copper thirteen 
parts, silver eleven; (2) copper one part, brass one, silver nine- 
teen; (3) brass five parts, zinc five, silver five. The flux for 
brass soldering is powdered borax, which may be mixed with 
water to a paste and applied with a feather or a small brush. 

Solder for Gold. — Gold soldering is the most particular 
work of this class which the dentist has to do. There are a 
few requirements for a good gold solder which might be noted 
and which are also applicable to the other solders mentioned: 
(1) The color should be as nearly as possible that of the metals 
upon which it is to be used. (2) The solder should have a 
fusing-point but very slightly below that of the metal to be sol- 
dered. (3) The solder should flow freely. 

Litch gives the following instructions for making a zinc-gold 
solder which will have the above-mentioned properties : 

" To make the zinc-gold solder take one pennyweight of the 
same gold upon which it is to be used and add one and a half 
grains of zinc. If this is done in a crucible in the furnace, first 
fuse the gold (which should either be clean scraps or be cut 
from the plate; never use filings for this purpose), using but little 
borax; when thoroughly fused take the crucible in the tongs, 
drop the zinc into it, give the crucible a rather vigorous yet 



132 DENTAL METALLURGY 

skilful shake to assist in mixing its contents, but without causing 
any to be thrown out, and immediately pour into the previously 
prepared ingot mold. This must be done very quickly or the 
solder will require too high a heat for the fusion on account of 
a large proportion of the zinc being volatilized or oxidized and 
thus be lost as alloys." 

Essig gives the following formulae for alloys of gold employed 
in dentistry as solders: 

No. i. 14 Carats Fine. No. 2. 14 Carats Fine. 

American gold coin $10.00 American gold coin. 16 dwts. 

Pure silver 4 dwts. Pure copper 3 " 18 grs. 

Pure copper _ 2 " Pure silver 5 " 

No. 3. 14 Carats Fine. No. 4. 15 Carats Fine. 

Pure silver 2\ dwts. Gold coin 6 dwts. 

Pure copper 20 grs. Pure silver 30 grs. 

Pure zinc 35 " Pure copper 20 " 

18-carat gold plate (formula Brass 10 " 

No. 11) ............ . 20 dwts. 

No. 5. 16 Carats Fine. No. 6. 16 Carats Fine. 

Pure gold n dwts. Pure gold n dwts. 12 grs. 

Pure silver 3 " 6 grs. Pure copper 1 dwt. 12 " 

Pure copper 2 " 6 " Pure silver 3 dwts. 

Pure zinc 12 grs. 

No. 7. 18 Carats Fine. 

Gold coin 3° P arts 

Pure silver 4 

Pure copper 1 part 

Brass 1 " 

No. 8. 20 Carats Fine, for Crown and Bridge Work. 

American gold coin (21.6 carats fine) $10 piece 258 grs. 

Spelter solder 20 . 64 " 

No. 9. 20 Carats Fine, Same Use as No. 8. 

Pure gold 5 dwts. 

Pure copper 6 grs. 

Pure silver 12 

Spelter solder 6 



FUSIBLE METALS AND SOLDERS 133 

No. 10. 20 Carats Fine, for Crown and Bridge Work. 

Zinc i£ grs. 

Pure gold 20 " 

Silver solder 3 " 

No. 11. Dr. C. M. Richmond's Solder for Bridge Work. 

Gold coin 5 dwts. 

Fine brass wire 1 dwt. 

No. 12. Dr. Low's Formula for Solder for Crown and Bridge 
Work, 19 Carats Fine. 

Coin gold 1 dwt. 

Copper 2 grs. 

Silver 4 " 

Solder for Platinum. — Platinum utensils may be soldered 
with any good gold solder, and a flux may be used if desired. 
When, however, the solder is used in connection with porcelain 
work, it must be pure gold or a gold and platinum alloy. A 
twenty-five per cent, platinum alloy has been found to give ex- 
cellent results. The folio wing in regard to gold and platinum 
alloy is from the Dental Review, August, 1905: 

" The colleges and text-books tell us the proper proportions of 
gold and platinum alloys, but they usually fail to tell us how 
to do it. In most cases the platinum appears in white spots 
on the plate without producing a proper alloy. Take a small 
piece of twenty- two-carat gold and fuse it under the blowpipe. 
Then work in all the platinum you can in small pieces until it 
has taken up all that is required. It will produce a small button 
of a white alloy which is very brittle. Add this alloy in required 
proportions to the gold in the crucible and it will produce a real 
platinum alloy. By this method you can make clasp gold that 
is pretty nearly as stiff as a steel spring and yet will roll and work 
without fracture." (Mark G. McElhinney, Ottawa, Canada.) 

Solder for Silver. — Solder for silver usually consists of 
alloys of silver and copper with sometimes zinc and sometimes 
tin. Litch recommends a silver solder made by alloying pure 



134 DENTAL METALLURGY 

silver with one-third its weight of brass. " Brannt's Metallic 
Alloys " gives alloys of silver and copper simply. Hall recom- 
mends silver eight parts, copper one, and zinc two. In the 
preparation of solder containing copper, zinc, or tin, the use of 
a flux is necessary to prevent the formation of metallic oxide. 
For this purpose borax is usually employed. The silver, con- 
stituting, as it does, the greater proportion of the alloy, should 
be melted first and be covered with considerable borax. When 
this has been thoroughly fused, the other metals may be added 
and mixed by agitation or by stirring with wood. Finally, the 
solder may be cast in the usual ingot mold. 



CHAPTER XV. 
DENTAL CEMENTS. 

Dental Cements may be classified as ordinary oxyphosphates 
of zinc cements, copper cements and synthetic cements which 
include the artificial enamels. These three kinds will include 
by far the larger proportion of cements in common use, and all 
contain more or less oxyphosphate of zinc. 

Oxyphosphate of Zinc. — The oxyphosphate cement is 
usually made by adding a powder, consisting largely of pure 
oxide of zinc, colored by a slight amount of other metallic ox- 
ides, to a liquid consisting of deliquesced phosphoric acid (or 
a solution of phosphoric acid in which zinc phosphate, and 
possibly slight amounts of other phosphates, have been dissolved), 
till a putty-like mass results, which rapidly hardens and becomes 
capable of receiving a considerable polish. When the phosphoric 
acid used is the glacial acid, the cement may be spoken of as a 
metaphosphate, because the glacial acid, before the addition of 
water, and to a certain extent afterwards, is actually metaphos- 
phoric acid, HP0 3 . The metaphosphoric acid by boiling with 
water or gradually by addition of water without boiling becomes 
the orthophosphoric acid (H 3 P0 4 ). 

Hall's Dental Chemistry takes the following tests from 
Flagg's Plastics and Plastic Filling, as characterizing a good 
oxyphosphate cement. 

General Tests, i . When first mixed it should yield a tough 
mass which when removed from the spatula does not adhere 
to the fingers and can be rolled into a pliable pellet. 

135 



136 DEXTAL METALLURGY 

2. It should have a glassy surface; and, at the end of two 
or three minutes, it should rebound when dropped upon wood, 
glass, or porcelain. 

3. At the end of five minutes it should be quite hard and 
should sound like porcelain when tapped. 

4. After ten or fifteen minutes it should be dented with 
difficulty, and when broken should show a clean, sharp fracture. 

5. After twenty minutes it should be very hard, and should 
be capable of taking a good burnish. 

6. In thirty minutes it should have little or no acid taste. 

Arsenic is a frequent impurity in both zinc oxide and phos- 
phoric acid, and if present is very liable to produce an irri- 
tating cement, sometimes causing considerable trouble; hence, 
the material entering into the composition of any dental 
cement should be free from arsenic (see pages 34 to 38 for arsenic 
tests) . 

The purer the zinc oxide and the phosphoric acid, from which 
the cement is made, the more durable it is found to be; so, aside 
from any question of irritation, it is quite necessary for the sake 
of the cement itself that the ingredients be pure. 

It is not intended to give the impression that the liquid should 
consist only of glacial phosphoric acid or the powder only of oxide 
of zinc. A cement thus made would set so rapidly that it would 
be of no practical value. The resulting mass would also prob- 
ably be crumbly. The powder or the liquid, one or the other, 
is usually mixed with phosphates of the heavy metals which 
would be insoluble in water, but which would dissolve in the 
strong phosphoric acid. 

A pure zinc oxide may be made by calcining the precipitated 
carbonate of zinc, Zn 5 (OH) 6 (C0 3 )2 + heat = 5 ZnO + 2 C0 2 + 
3 H 2 0. The heat should be below 500 F., because, if too strongly 
heated, the color suffers, becoming yellowish. 

Another method of making pure oxide of zinc is given as 
follows: Dissolve pure zinc in nitric acid, evaporate to dryness, 



DENTAL CEMENTS 137 

and heat till fumes cease to be given off. The mechanical effect 
of the escaping oxides of nitrogen is said to leave the zinc oxide 
in the form of a very fine powder. 

A pure phosphoric acid can be made from the ortho-acid 
by heating till the white fumes begin to come off, then heating 
to redness, cooling and dissolving in water to a thick syrup. In 
mixing cements, the powder should be worked into the liquid 
till the desired consistency is obtained. 

Oxyphosphate cement and all cements having zinc oxide for 
a base tend to dissolve in the fluids of the mouth, lactic acid and 
ammonium salts being particularly good solvents for this class 
of compounds. The addition of ferric oxide to oxyphosphate 
cement increases resistance to disintegration. One part of 
ferric oxide to six to ten of zinc oxide is recommended by Rollins 
in the International Dental Journal. 

Oxychloride of Zinc is more easily soluble than oxyphos- 
phate. It shrinks more, but is credited with a preservative 
action on dentine and hence is used to some extent as a lining. 

The powder of the oxychloride cement is zinc oxide with 
sometimes a little borax, or silica, or both, added. A good 
oxychloride cement will set in fifteen or twenty minutes, but 
keeps on growing harder for several hours. The following 
formula is recommended. 

Oxide of zinc 10 grams, borax 0.1 gram, and powdered silica, 
0.2 gram. 

Transfer to clay crucible and calcine for one-half hour in 
furnace at bright-red heat. Pulverize, sift, and bottle. The 
liquid to be used with this powder consists .of 10 c.c. of pure 
hydrochloric acid saturated with pure zinc and filtered through 
glass wool. 

Oxysulphate of Zinc. — This is used still less than the oxy- 
chloride. It is non-irritating, dissolves easily, and is compara- 
tively soft. The following formula is taken from Hall's Dental 
Chemistry. 



138 DENTAL METALLURGY 

Ten grams oxide of zinc, four grams sulphate of zinc. Dry, 
mix, calcine for one-half hour, and sift. 

Liquid to be used with the powder may be made by dissolv- 
ing two grams of zinc chloride in 10 ex. of water. This gives a 
turbid solution and should be shaken when used. 

Oxyphosphate of Copper cement (Ames's) consists of the 
usual powder and liquid. The powder contains oxides of cop- 
per, iron (slight amount), cobalt, and zinc, and, of course, is 
black in color. The liquid is phosphoric acid holding in solution 
a certain amount of phosphate of zinc. 

The cement resulting from this combination was found to 
be hard, showing practically no change of volume and resisting 
the solvent action of the saliva. 

White Copper cement. The powder of this preparation has 
been found to consist of 95% oxide of zinc and 5% of cuprous 
iodide.* The presence of iodine can be easily demonstrated 
by treatment with nitric acid and the solution of the iodine in 
chloroform. 

Tin cement. Dr. Arthur Scheuer, of Teplitz, Bohemia, recom- 
mends a preparation composed of a finely pulverized tin sponge 
and zinc oxide mixed with glacial phosphoric acid. " The powder 
is of a light-gray color, becoming slightly darker when mixed with 
the acid, but regains its original color after setting. A tin- 
cement filling can be easily inserted and when polished it has a 
metallic appearance." (Dental Cosmos, May, 1904.) 

Artificial Enamel. — Several preparations have been put on 
the market under this name, in each case with the claim that it 
makes a much harder cement and one which resists disintegra- 
tion to a much greater extent than the ordinary zinc preparations. 

The specifications of a German patent, under which one of 
these preparations is manufactured, claim that the powder con- 
sists of a mixture of the oxides of beryllium and silicon, together 
with alumina and lime. The liquid consists of a 50% solution 
* W. V. B. Ames, D.D.S., Dental Review, June, 1914. 






DENTAL CEMENTS 139 

of orthophosphoric acid in which aluminium phosphate and 
zinc phosphate have been dissolved. 

A qualitative analysis confirms the claim of the patent spe- 
cifications both in regard to the composition of the liquid and 
the presence of oxide of beryllium in the powder, and it is prob- 
able that the value of these preparations depends largely upon 
the proportion of beryllium entering into their composition. 

This statement from an earlier edition has been quoted* 
with the assertion that about one-quarter of the powder of 
Ascher's artificial enamel is beryllium oxide. 

Beryllium is a rare metal which occurs naturally with alumin- 
ium as a silicate, also as beryllium silicate (beryl), colored forms 
of which are used as precious stones. Beryllium forms basic 
compounds of such character as makes it suitable for use in 
dental cement. 

The cement powders may be tested for beryllium as fol- 
lows: Fuse a little of the powder with sodium carbonate (or 
the double sodium potassium carbonate); dissolve the fused 
mass in dilute hydrochloric acid; evaporate to dryness and 
heat to 120 C. to dehydrate the silica; take up in water with a 
little hydrochloric acid and filter; to the filtrate (probably con- 
taining Al, Be, Zn, and Ca) add a little ammonium chloride, 
and an excess of ammonium carbonate, Al(OH) 3 , Be(OH) 2 , and 
CaC0 3 , will be precipitated. The beryllium, however, is easily 
soluble in the excess of (NH^CC^. Warm (not boil) and allow to 
stand for some time to insure complete separation of aluminium. 

{Note. — Al(OH) 3 is much less soluble in solution of (NH4) 2 C0 3 than in either 
NEUOH or even NH4OH and NH4CI.) 

Filter. Boil the filtrate for a long time, when the beryllium and 
some zinc will be precipitated. Filter and dissolve precipitate 
off paper in dilute hydrochloric acid. To the filtrate containing 
BeCl 2 and ZnCl 2 add NH 4 C1 in excess and NH4OH, which will 

* Dental Summary, 1915, p. 56. 



140 DENTAL METALLURGY 

give a precipitate of Be(OH) 2 . If beryllium and zinc only are 
present, the separation by boiling may be unnecessary. 

The liquid may be tested for dissolved phosphates by dilut- 
ing with water and adding ammonia till alkaline; if the mixture 
remains clear, phosphates of alumina, calcium, or zinc are 
absent. Care should be used, however, in the addition of the 
ammonia, as an excess of this reagent will redissolve phosphate 
of zinc. 

If the ammonia is too strong, a precipitate of ammonium 
phosphate may be obtained, but this may be easily redissolved 
by the simple addition of water. 

Silicate cements, synthetic cements, and synthetic porcelain 
are names applied to later preparations containing silica, alu- 
minium, and sometimes magnesia in addition to usual cement 
constituents. Dr. Ames is authority for the statement that 
beryllium is useful chiefly for advertising purposes. 

It might be well to remember in this connection that the 
natural sources (ores) of beryllium available in Europe are 
richer in beryllium than those obtained in this country. 

Dr. E. O. Hile, in the Dental Digest for 1913, page 441, says 
that the production of de Trey's synthetic porcelain is based 
upon a study of the setting of Portland cement. The liquid of 
this porcelain contains a smaller proportion of acid than any 
cement liquid. 



CHAPTER XVI. 
RECOVERY OF RESIDUE. 

Gold. — The gold scrap may be recovered in two ways : 
first, by fusion with suitable flux; second, by dissolving in aqua 
regia and precipitation of the metal. In the first method it 
is necessary to remove mechanically the impurities as far as pos- 
sible, then mix the fairly clean gold waste with potassium nitrate 
and a little borax, and fuse in a clay crucible. The gold will 
separate as a button at the bottom of the thoroughly fused slag. 

In the second method the scrap gold is dissolved in aqua 
regia and the resulting solution of gold chloride is precipitated 
with ferrous sulphate or oxalic acid. The latter precipitant, al- 
though working more slowly than the iron, does not precipitate 
platinum, hence in case platinum is present it is the better re- 
agent to use. The precipitated gold is next filtered, thoroughly 
washed, and fused in clay crucible under borax and potassium 
nitrate. 

Silver. — The recovery of silver is best accomplished by 
dissolving the scrap or waste in nitric acid and precipitating as 
chloride, then reducing the chloride to metallic silver either by 
treatment with pure zinc or by fusion with sodium carbonate. 
If tin is present in the scrap, the nitric acid will form me tas tannic 
acid, a white insoluble powder rather difficult to filter. Hence, 
it is better to wash this by decantation several times with dis- 
tilled water, which will remove practically all the silver. From 
the nitric-acid solution the silver may be precipitated by salt or 
hydrochloric acid. This precipitate must be washed till the 
wash-water is practically free from chlorine, then dried and fused 

141 



142 DENTAL METALLURGY 

with sodium carbonate, when a button of pure silver will be ob- 
tained. 

If preferred, the precipitated chloride of silver may be washed 
once by decantation, then agitated with pure zinc, when the 
following reaction takes place: 

2 AgCl + Zn = ZnCl 2 + 2 Ag. 

The finely-divided silver (in the form of nearly black powder) 
must be washed free from chlorine, carefully dried and fused 
under carbonate of sodium, or, after drying, it may be weighed 
and dissolved at once if a solution is desired. If the silver residue 
contains mercury this may be driven off by heat before solution 
is attempted. 

Mercury. — Mercury which has been used in making amal- 
gams is best purified by distillation. Mercury which needs 
simply to be freed from dirt, dust, or slight traces of other 
metals may be purified as follows: If a piece of filter-paper is 
fitted closely in a glass funnel, a pin-hole made in the joint 
and the paper thoroughly wetted with water and the mercury to 
be purified placed on the paper, the heavy metal will run through 
the pin-hole, leaving practically all the dirt clinging to the wet 
filter-paper. Such mercury may also be cleansed by filtering 
through chamois-skin. 

In case the mercury contains slight amounts of other metals, 
if it is digested with a very dilute nitric acid, the acid will gen- 
erally first dissolve the impurities and afterwards a little of the 
mercury itself. Then thorough washing with water will remove 
all excess of acid and all soluble salts which may have been 
formed. Pure mercury should have no coating of any sort on 
its surface, and if a few globules are allowed to run down a 
smooth inclined plane, they should leave no " tail " behind. 



PART III. 
VOLUMETRIC ANALYSIS. 

CHAPTER XVII. 
STANDARD SOLUTIONS. 

Volumetric analysis is the determination of the quantity 
of a particular substance contained in a given sample by means 
of volumetric or standard solutions. By means of standard 
solutions, it is possible to determine easily and quickly the 
strength of a peroxide of hydrogen solution, the percentage of 
silver in an amalgam alloy, or the amount of gold in a plate 
or solder, and it is volumetric analysis thus specialized and 
adapted to dental purposes that we shall consider. 

The standard solution may be so prepared that it has an 
arbitrary or special value, such, for instance, as the silver-nitrate 
solution usually used in determining the amount of chlorine 
in urine, i c.c. of this solution being equal to ten milligrams of 
salt (NaCl) ; or its standardization may be made with reference 
to the molecular weights of the reagents employed, so that solu- 
tions of a similar nature will be of equivalent values. 

Normal and decinormal solutions, or the volumetric solutions 
of the U. S. P., are of this character. 

A normal solution may be defined as one containing the 
hydrogen equivalent of the reagent in grams per liter. This 
definition may be explained by saying that the solution contains 
the molecular weight of the reagent in grams per liter provided 
the reagent is of univalent basicity; otherwise such part of the 
molecular weight is taken as shall represent the molecule reduced 
to a univalent basicity. 

143 



144 VOLUMETRIC ANALYSIS 

For example, a normal (N/i) solution of hydrochloric acid 
or of potassium hydroxide would contain the molecular weight 
per liter; one of sulphuric acid or of calcium hydrate would 
contain one-half the molecular weight per liter. 

If the process involves oxidation, the oxidizing power of the 
reagent relative to one atom of hydrogen determines the pro- 
portion of the molecular weight to use; for example: iodine (I 2 ) 
and hydrogen peroxide (H2O2) will each require half the molec- 
ular weight per liter to make a normal solution because in each 
case the molecule will " oxidize " two atoms of hydrogen. So 
K 2 Mn 2 8 , which will furnish five atoms of available oxygen 
capable of oxidizing ten atoms of hydrogen, requires only one- 
tenth of its molecular weight in 1000 c.c. to produce a normal 
solution. 

It will be seen from the above explanation that equal volumes 
of normal solution will always bring about exact reactions. 

The normal solution should not be confused with molar 
(M/i) solution used elsewhere in the book, which contains the 
molecular weight of the reagent in grams per liter without regard 
to the hydrogen equivalent; for example: a molar solution of 
H2SO4 contains ninety-eight grams, while a normal solution 
contains forty-nine grams per liter. 

Exact reactions between molar solutions are produced when 
volumes corresponding to the respective number of molecules 
taking part in the reaction are used. See Exp. 16, page 371. 

The normal factor is the weight of reagent contained in one 
cubic centimeter of the normal solution. 

The volumetric process and the use of the normal factor 
will be most clearly understood by the explanation of a specific 
example. 

We will suppose that we have prepared a normal solution of 
NaOH and wish to ascertain the strength of a sample of dilute 
HC1. The normal solution will contain the molecular weight 
in grams of NaOH per liter or forty grams absolute NaOH. 



STANDARD SOLUTIONS 145 

The molecular weight of HC1 being 36.4 (36.37), a normal 
solution of HC1 will contain 36.4 grams absolute HC1; and, if 
a liter of normal NaOH were added to a liter of normal HC1, 
exact neutralization would result: 

NaOH + HC1 - NaCl + H 2 0. 
40 36.4 58.4 18 

The one liter of normal alkali (containing 40 grams NaOH) 
is exactly neutralized by 36.4 grams of HC1, or 1 ex. of normal 
alkali by 0.0364 gram of HC1. 0.0364 is normal factor of 
HC1. 

Now, if by our process of. analysis we find that it takes just 
21 c.c. of the NaOH solution to exactly neutralize 10 c.c. of 
HC1 solution, 1 c.c. of NaOH being equal to 0.0364 gram HC1, 
21 c.c. of NaOH will be equal to 0.0364 X 21, or 0.7644 gram 
HC1, or 10 c.c. of the HC1 solution contains 0.7644 gram of 
absolute HC1, equivalent, approximately, to 7.64%. 

It has become apparent that in carrying out this process 
three things are absolutely necessary: 

1. Methods for the preparation of standard solutions. 

2. Apparatus for accurate measurements of both the standard 
solution and the unknown. 

3. Means for determining just when the point of exact 
neutralization is reached. This point is known as the " end 
point " and is shown by " indicators " of various kinds. 

Preparation of Standard Solutions. — Experience has shown 
that normal solutions are in many cases less convenient to work 
with than those much more dilute, both on account of the keep- 
ing qualities of the standard solution and the accuracy of manip- 
ulation; and, for the purposes of dental chemistry, a decinormal 
or one- tenth normal solution represented by N/10 will generally 
be used. 

In working with an N/10 solution, the factor used in cal- 
culations of results will be one-tenth of the normal factor and 



146 VOLUMETRIC ANALYSIS 

is termed an N/10 factor. Other fractional proportions of the 
normal solution may be used as the centinormal, N/100, or 
seminormal, N/2. While the decinormal solution contains 
one-tenth of the hydrogen equivalent of reagent in grams per 
liter, and this amount is very easy to calculate, it is often very 
difficult to weigh out the exact amount required. For instance, 
we want an N/10 solution of HC1. HC1 is a gas soluble in 
water and the strengths of the solutions vary greatly, so we can- 
not weigh out 3.637 grams of absolute HC1 to put in 1000 c.c. of 
water though we know this is just the amount necessary to 
produce our N/10 solution. Thus, one of the first practical 
difficulties in making up standard solutions is to find some sub- 
stance which can be weighed accurately and the exact chemi- 
cal composition of which may be relied upon. 

Crystallized oxalic acid is such a compound, although care 
must be taken that the crystals are dry and yet contain all 
their water of crystallization; in other words, are actually 
represented by the formula H 2 C20 4 ,2 H 2 0. Fused carbonate of 
sodium is another such compound. If the purest obtainable 
bicarbonate of soda is fused till no further change takes place, 
cooled, and powdered, the product is pure enough for the prep- 
aration of a standard solution for ordinary use. 

For the preparation of volumetric solutions it is necessary to 
have a balance which will weigh accurately to at least two 
decimal points. It will be much better to have a balance sen- 
sitive to one milligram. Balances of this sort inclosed in a glass 
case can be obtained at a very reasonable price. Fig. 12 on 
page 147 represents such a balance. 

It is also essential to have flasks capable of holding 100, 250, 
500, and 1000 c.c. carefully graduated on the neck, represented 
in Fig. 13, page 147. 

Graduated cylinders (Fig. 14) are not so well suited for the 
preparation of standard solutions, as the greater breadth of the 
column of liquid makes accurate reading much more difficult. 



STANDARD SOLUTIONS 



147 




Fig. 12. 



Fig. 13. 




I 



I 




Fig. 14. 



Fig. 15. 



Fig. 16. 



148 VOLUMETRIC ANALYSIS 

Small cylinders of 100 c.c. or less are useful in making up 
odd amounts of solution. 

In the process of analysis it will be necessary to have pipettes 
(Fig. 15) measuring 5 and 10 c.c, also a burette (Fig. 16), from 
which the standard solution may be used. The burettes may 
be had in a variety of styles and sizes, a very serviceable one 
being of 25 c.c. capacity and graduated in tenths of a cubic centi- 
meter. It may have a glass stop-cock or it may be furnished 
with a glass tip with rubber connector and pinch-cock. 

A set of measuring-instruments which have been carefully 
compared with one another should be kept; that is, the 1000-c.c. 
flask should be exactly filled by taking the 100-c.c. flask full to 
the mark just ten times, thus enabling one accurately to take 
aliquot parts of any given solution. 

Indicators. 

The third requisite for carrying out a volumetric process 
is a method for determining the end point of the reaction; that 
is, we must know when there has been a sufficient quantity 
of a standard solution added to an unknown solution. Phenol- 
phthalein gives a red color with alkalis, which is discharged 
by the addition of acid till the solution becomes colorless as it 
becomes neutral or acid. Litmus gives a blue color with al- 
kalis and a red with acids; Methyl orange can be used with 
carbonates and mineral acids; it does not work so well with 
organic acids. The color is pink in acid and yellow in alka- 
line solution. Lacmoid is useful in cases where the acid prop- 
erties of such salts as alum or zinc chloride might interfere with 
the use of litmus or phenolphthalein. The different indicators 
do not all change color at exactly the same point in the process 
of neutralization, and it is possible for a solution to be alkaline 
to litmus and acid to phenolphthalein at the same time. Hence 
uniformity in the use of indicators is desirable. In physiological 



STANDARD SOLUTIONS 149 

chemistry, congo red, tropaeolin 00, and dimethylaminoazoben- 
zene are also used. 

The end point may be indicated by excess of a standard 
solution if it happens to be highly colored, as potassium per- 
manganate. Thin starch paste is used as an indicator in oper- 
ations involving the use or liberation of free iodine. Other 
indicators will be considered as we have occasion to use them in 
the various analytical processes. 

The processes of volumetric analysis may be divided into 
three classes: First, acidimetry and alkalimetry. Second, oxi- 
dation and reduction. Third, precipitation. 

Acidimetry and Alkalimetry. 

Acidimetry and alkalimetry includes all standardized solu- 
tions, either acid or alkaline, which may be used in neutralizing 
solutions of unknown strength of an opposite character. For 
instance, the strength of vinegar is determined by neutralizing 
a known volume with standard alkali. 

For present purposes two standard acids and one standard 
alkaline solution will be sufficient. 



DECINORMAL OXALIC ACLD. 

The first of these may be decinormal oxalic solution prepared 
from recently recrystallized and carefully dried acid. The 
composition of these crystals should be H2C2O4.2 H 2 0, having 
molecular weight of 126. 

If we consider the reaction involved in the neutralization 
of oxalic acid (H 2 C 2 4 + 2 NaOH = Na 2 C 2 4 + 2 H 2 0) we see 
that twice as much alkali is required as would be necessary to 
neutralize a monobasic acid like HC1. Hence to obtain our 
hydrogen equivalent we divide the molecular weight of oxalic 
acid by two, which will give us a weight in grams to be dis- 



150 VOLUMETRIC ANALYSIS 

solved in sufficient water to make one liter of normal solution. 
A decinormal solution will be one- tenth of this strength. 

For class use, each student may prepare 500 c.c. of this 
solution by dissolving 3.15 grams of pure crystallized oxalic 
acid in water and dilute to a half-liter. The graduated flasks 
are usually constructed to be used at a temperature of 6o° F. 
or 1 5 C. and for accurate work solutions must be brought 
to this temperature. After the oxalic acid solution has been 
prepared the decinormal alkali may be made as follows: 

DECINORMAL SODIUM HYDROXIDE. 

Weigh out carefully two and a half grams of caustic soda or 
three grams of caustic potash and dissolve in less than 500 c.c. of 
distilled water. After the solution has thoroughly cooled, fill a 
burette with it. Place 10 c.c. of standard acid previously 
prepared in a white porcelain dish of about 250 c.c. capacity, 
add 20 c.c. distilled water and two or three drops of phenol- 
phthalein (2% phenolphthalein in alcohol and water, equal parts) ; 
then carefully run in from the burette, with constant stirring, 
the alkali solution until a permanent pink tint is produced. 
This process is known as " titration," and will hereafter be so 
designated. 

The work will be more satisfactory if the titration is made 
for the appearance of color rather than the disappearance of 
color, as would have been the case had the standard acid run 
into the measured alkali solution. 

The Calculation. — Supposing it has taken 8.2 c.c. of the 
alkali to exactly neutralize the 10 c.c. of N/10 acid, it follows that 
in the 8.2 c.c. there is sufficient alkali to equal or to make 10 c.c. 
of an N/10 alkali solution; hence we may add 1.8 c.c. of 
distilled water to every 8.2 c.c. of alkali solution, thereby 
reducing it to decinormal strength. Practically we should take 
410 c.c. of alkali solution and in a graduated flask make it up to 
500 c.c. with distilled water. It will be necessary to make 



STANDARD SOLUTIONS 15 1 

several titrations and average the results before making the 
calculation. 

From the standard alkali N/10 solutions of HC1 or H 2 S0 4 
may be prepared in a similar manner, it being impossible to 
accurately weigh either of these two acids. In titrating a car- 
bonate, if an indicator, such as phenolphthalein, which is sensi- 
tive to carbonic acid, is used, it is necessary to keep the solution 
at a boiling temperature or at least bring it to a boil after every 
addition from the burette. 

VOLUMETRIC DETERMINATION OF ACETIC ACID. 

As an example of acidimetry and alkalimetry determine the 
strength of a sample of vinegar as follows: 

Measure accurately into a white porcelain dish of 150-250 
c.c. capacity 1 c.c. of the sample. This may be measured either 
with a carefully graduated i-c.c. pipette or more accurately 
by diluting 10 c.c. of the sample to 100 c.c. in a graduated flask, 
then using 10 c.c. of the dilution for the titration, the titration 
to be performed with N/10 NaOH, using phenolphthalein as an 
indicator. 

The molecular weight of acetic acid is, in round numbers, 
60; hence the N/10 factor of acetic acid will be 0.006 (acetic acid 
being monobasic, HC 2 H 3 2 ). To ascertain the strength of the 
sample of vinegar it is necessary to multiply the number of 
cubic centimeters used by this factor, 0.006, which will give 
the amount of absolute acid calculated as acetic in 1 c.c. (prac- 
tically 1 gram) of the sample. Thus, if 8 c.c. of N/10 alkali 
were required to neutralize 1 c.c. of vinegar, multiplying the 
factor 0.006 by 8 would give 0.048 gram of absolute acetic acid 
in 1 c.c. of vinegar, which is equivalent to 4.8%. 

VOLUMETRIC SOLUTION OF HYDROCHLORIC ACID. 

The volatile character of hydrochloric acid renders a solution 
of normal strength rather unstable, so decinormal or weaker 



152 VOLUMETRIC ANALYSIS 

solutions of this acid are commonly employed. Take a solution 
of hydrochloric acid which shall contain four to four and one-half 
grams per liter. Make several titrations with decinormal so- 
dium hydroxide and from the average of these dilute to decinor- 
mal strength as follows: the acid solution has been made rather 
stronger than decinormal so the 10 c.c. of dilute HC1 may have 
required 12.5 c.c. of standard alkali for exact neutralization. In 
this case add 250 c.c. of distilled water to 1000 c.c. of the acid. 

DETERMINATION OF MAGNESIUM HYDRATE OR MILK 
OE MAGNESIA. 

The strength of milk of magnesia may be volumetrically 
determined as follows: To five grams of carefully mixed and 
accurately weighed milk of magnesia add twenty-five cubic 
centimeters of normal sulphuric acid. When dissolved, dilute 
the solution to 250 c.c. Mix thoroughly and titrate 25 c.c. 
of this solution with decinormal alkali. The result of this 
titration multiplied by ten will give the uncombined acid. 
Subtract this from the volume of standard acid originally used 
and calculate the amount of Mg(OH) 2 . Each cubic centimeter 
of the normal acid corresponds to 0.02917 gram of magnesium 
hydroxide. 

Note. — This process is based upon the last revision of the United States 
Pharmacopoeia in which the term cubic centimeter is everywhere replaced by the 
name mils. This term indicates a milliliter or one-thousandth of a liter, which the 
revisers consider to be more accurate than cubic centimeter. 

CARBONATE TITRATION. 

While perhaps phenolphthalein is the most serviceable of all 
indicators in common use, it is so sensitive to carbon dioxide that 
any titration which results in the liberation of C0 2 must be 
modified by boiling the solution thoroughly after each addition 
of acid. This makes the operation somewhat tedious, but it is 
to be preferred to the use of other and less sensitive indicators 
which may not be affected by the carbon dioxide. 



STANDARD SOLUTIONS 153 

Analysis by Oxidation and Reduction, 
decinormal permanganate of potassium. 

If to a hot solution of oxalic acid containing sulphuric acid, 
permanganate of potash be added, the following reaction takes 
place: 

2 KMn0 4 + 5 H 2 C 2 4 + 3 H 2 S0 4 - K 2 S0 4 + 2 MnS0 4 
+ 10 C0 2 + 8 H 2 0. 

This reaction represents a very valuable method of volumetric 
analysis; but, inasmuch as it is not a process of neutralization, 
it cannot properly come under the head of acidimetry and alka- 
limetry, but rather under a distinct classification, the determina- 
tion involving oxidation and reduction. 

Standard Permanganate Solution. — In the reaction given 
above we may consider that, as the molecule of K 2 Mn 2 8 breaks 
up, three of the eight atoms of oxygen are required to form the 
basic oxides K 2 and 2 MnO (soluble in the acid as K 2 S0 4 and 
2 MnS0 4 ), while the remaining five atoms are liberated and 
constitute the active chemical agent whereby the oxalic acid is 
oxidized to C0 2 and H 2 0. Hence, to reduce this double molec- 
ular weight (316) to the hydrogen equivalent necessary for a 
normal solution, it is divided by 10 (five atoms of oxygen having 
a valence of 10). 

The Decinormal Solution may be made by dissolving 3.16 
grams of pure recrystallized and thoroughly dried crystals, if 
they can be obtained, in distilled water, and making the solu- 
tion up to 1000 c.c, or it may be standardized by titration with 
the N/10 oxalic acid previously prepared; in this case one would 
proceed as follows : 

Make a solution slightly stronger than the standard required, 
say about 3.5 grams of the ordinary pure crystals in a liter of 
water; with this fill a burette, place 10 c.c. of N/10 oxalic acid 
measured from a pipette in an evaporating-dish or casserole, 
dilute with about 50 c.c. of water, add about 10 c.c. of dilute 



154 VOLUMETRIC ANALYSIS 

sulphuric acid, and heat the mixture nearly to the boiling-point. 
Then titrate with the permanganate from the burette. The 
permanganate will at first be rapidly decolorized, but as the 
operation progresses the color fades more slowly till at last a 
faint permanent pink color indicates that the " end point " has 
been reached. 

The temperature must be kept above 6o° C. throughout the 
titration or the oxidation will take place too slowly and an 
apparent end point will be obtained before the reaction is com- 
pleted. 

If the solution turns muddy during the operation, it is due 
to an insufficient amount of sulphuric acid and more should 
be added. The calculation is made as in the case of the N/io 
NaOH described on page 150. The standard permanganate 
should be preserved in full, well-stoppered bottles and kept in a 
dark place. 

It is better to have the KMn0 4 solution made up a day or 
two before it is standardized, thereby allowing for oxidation of 
traces of ammonia, etc., which the water may contain. 

DETERMINATION OF PEROXIDE OF HYDROGEN. 

In determining the strength of peroxide use 1 c.c. of the 
sample measured, as in the case of vinegar (which see), dilute 
with 50 c.c. of distilled water, add 10 c.c. of dilute sulphuric 
acid, and titrate with the permanganate in exactly the same 
manner as detailed in the preceding paragraph, with the excep- 
tion that the titration must be made cold. The reaction takes 
place so easily that heat is unnecessary and even a slight elevation 
of temperature may result in loss of hydrogen peroxide, the reac- 
tion in this case being as follows: 

2 KMn0 4 + 5 H 2 2 + 3 H2SO4 = K 2 S0 4 + 2 MnS0 4 + 5 2 
+ 8 H 2 0. 

The aqueous solutions of peroxide on the market used as 



STANDARD SOLUTIONS 155 

antiseptics contain about 3% absolute H 2 2 and yield approxi- 
mately ten volumes of available oxygen; that is, 10 c.c. of solu- 
tion will yield 100 c.c. of oxygen. The calculation may be 
made to express N strength of the peroxide in terms of percentage 
of absolute H 2 2 by multiplying the number of cubic centimeters 
of N/10 KMn0 4 decolorized by 1 c.c. of solution by 0.17, or to 
express the strength in volumes of available oxygen by multiply- 
ing the number of cubic centimeters of solution by 0.56 (more 
accurately 0.5594). 

DECINORMAL IODINE 

A decinormal solution of iodine may be prepared by dissolv- 
ing 12.68 grams of pure iodine crystals in one liter of water 
by the aid of about 18 grams of pure potassium iodide. 

Iodine of sufficient purity may be obtained by carefully re- 
subliming selected and carefully dried crystals of so-called 
" chemically-pure " iodine. 

DECINORMAL SODIUM THIOSULPHATE. 

Na 2 S 2 3 .5 H 2 0, molecular weight = 248.24. This solution 
may be made by weighing directly 24.824 grams of the pure 
crystallized salt, dissolving in water and diluting to 1000 c.c, or 
it may be standardized by titration with a decinormal iodine 
solution, the reaction being as follows : 

2 Na 2 S 2 3 + 2 I = 2 Nal + Na 2 S 4 6 . 

The indicator used is a very dilute starch paste, which gives 
the characteristic blue color as soon as free iodine is in excess. 

By means of these two standard solutions (iodine and sodium 
thiosulphate) a variety of determinations may be made with 
great accuracy. Any substance which will liberate iodine from 
potassium iodide may be quantitated by adding an excess of 
the potassium salt and titrating the free iodine with thiosulphate 
solution, using starch paste as usual for an indicator. 

Peroxide of hydrogen may be thus determined as easily as 



156 VOLUMETRIC ANALYSIS 

by the permanganate method previously given. The process, 
being that of Kingzett, is given as follows by Sutton : 

Mix 10 c.c. of peroxide solution to be examined with about 
31 c.c. of dilute sulphuric acid (1-2) in a beaker, adding crystals 
of potassium iodide in sufficient quantity, and after standing 
five minutes titrating the liberated iodine with N/10 thiosul- 
phate and starch. The peroxide solution should not exceed the 
strength of two volumes; if stronger, it must be diluted pro- 
portionately before the analysis. 

In the case of a very weak solution it will be advisable to 
titrate with N/100 thiosulphate. 

1 c.c. N/ 10 thiosulphate = 0.0017 gram H 2 2 . 

DETERMINATION OF IODINE SOLUTION. 

Titrate 10 c.c. of the iodine solution with standard sodium 
thiosulphate until the iodine color has become a pale yellow; 
then, and not until then, add the starch paste indicator and con- 
tinue titration until blue color is discharged. 

DETERMINATION OF HYPOCHLORITE SOLUTION. 

By the use of sodium thiosulphate the strength of chlorinated 
lime, used as a disinfectant, may be easily determined. The 
following process is based upon the assay given in the nine- 
teenth revision of the Pharmacopoeia (19 16). 

Into a small, tared, stoppered, weighing bottle containing 
10 c.c. of distilled water introduce about two grams of chlo- 
rinated lime and weigh carefully. In a small mortar rub this 
mixture with repeated portions of water which are to be carefully 
transferred to a 500-c.c. graduated cylinder. When one or two 
hundred c.c. of water have been used in this way rinse the 
weighing flask and mortar several times with distilled water, 
adding the rinsings to the graduated cylinder, and finally making 
the entire volume measure exactly 500 c.c. Mix thoroughly 






STANDARD SOLUTIONS 157 

and allow to settle. Take twenty-five to fifty c.c. of this mix- 
ture accurately measured, transfer to a porcelain dish, add half a 
gram of potassium iodide and two to three c.c. of acetic acid and 
titrate with decinormal sodium thiosulphate solution, using 
dilute starch solution as an indicator. Each cubic centimeter 
of the standard thiosulphate corresponds to 0.003546 of a gram 
of available chlorine. 

Note. — The strength of metallic peroxides may be determined by acting 
upon the peroxide with hydrochloric acid, conducting the liberated chlorine into 
a potassium iodide solution and titrating the liberated iodine with standard 
thiosulphate. 

VOLUMETRIC DETERMINATION OF ARSENIC. 

Mohr's method of oxidation with iodine is a practical one. 
The titration is made with N/10 iodine and starch as usual, 
except that the solution should be at first neutral and then 
about 20 c.c. of saturated solution of sodium bicarbonate should 
be added to every 0.1 gram of As 2 3 supposed to be in the un- 
known, thus giving a certain definite alkalinity. If the solution 
is acid, neutralize with sodium bicarbonate, then make alkaline 
with more bicarbonate as above. 

VOLUMETRIC DETERMINATION OF GOLD. 

While gold is usually determined quantitatively by assay 
in a dry way (page 164) it may be determined very accurately 
by titration with thiosulphate solution. Fatka (Chem. Zeit.) 
recommends the following process based upon the fact that 
a neutral solution of gold salt with potassium iodide will give 
a greenish precipitate. When an excess of potassium iodide 
is used no precipitate is formed, but a solution of Aul 3 as AuKLi 
results. This is of a brown color and may be titrated with 
N/10 thiosulphate solution, when the following reaction takes 
place : 

AUKI4 + 2 Na 2 S 2 3 = AuKI 2 + 2 Nal + Na 2 S 4 6 . 



158 VOLUMETRIC ANALYSIS 

Process: 10 c.c. of gold solution containing approximately 
2 % of gold is treated with 4 grams of potassium iodide diluted 
to 100 c.c. with water and titrated with N/10 Na 2 S 2 3 solu- 
tion, using starch as an indicator. 

VOLUMETRIC DETERMINATION OF GOLD. 

(Second Method.) 

In the analysis of dental alloy, gold will remain undissolved 
by HNO3 and will be weighed with the Sn0 2 . It should be sep- 
arated and its weight deducted before calculation is made for 
tin. This may be done by dissolving the gold in dilute aqua 
regia, evaporating the solution of gold chloride to dryness, dis- 
solving residue in distilled water and proceeding according to fol- 
lowing method from Schimpf's Manual of Volumetric Analysis. 

The gold must be in the form of chloride (AuCla). 

To the solution of gold chloride a measured excess of N/i 
oxalic acid solution is added and the mixture set aside for twenty- 
four hours. 

The solution is then made up to a definite volume (say 300 
c.c). Then, by means of a pipette, 100 c.c. are removed, and 
the excess of oxalic found by titrating with N/10 permanganate 
in the presence of sulphuric acid. The reaction is 

2 AuCla + 3 H 2 C 2 4 = 2 Au + 6 HC1 + 6 C0 2 . 

Each cubic centimeter of N/i oxalic acid solution = 0.06523 
gram of Au, or 0.1004 gram of AUCI3. 

Analysis by Precdpitation. 

Because certain elements possess a selective affinity for 
other elements it is possible to determine many substances 
quantitatively by precipitation. That is, if silver nitrate is 
added to a mixture of a soluble chloride and a chromate, the 
chlorine will combine first with the silver, forming AgCl, to the 
exclusion of the chromate. After the last trace of chlorine has 



STANDARD SOLUTIONS 159 

been so combined, the silver chroma te will be formed, which 
is a salt with an intense red color; hence it is possible to 
determine the strength of solutions of soluble chlorides by titra- 
tion with standard AgN03, using potassium chromate as an in- 
dicator. This process is used in analysis cf drinking-water, of 
saliva, and of urine, but for each of these it is desirable to have 
solutions of special strength. 

A DECINORMAL SILVER SOLUTION 

may be made by dissolving seventeen grams of pure crystallized 
AgN0 3 in a liter of distilled water, and with this a 

DECINORMAL SODIUM CHLORIDE SOLUTION 

may be prepared as follows: 

Weigh out six grams of the purest salt obtainable and dis- 
solve in approximately one liter of distilled water. With a 
pipette measure 10 c.c. of this solution into a white porcelain 
dish, dilute to about 20 c.c. with H 2 0, add two to five drops of 
neutral potassium chromate (K 2 Cr0 4 ) and add AgN0 3 from a 
burette till a faint pink color persists. 

The calculation and dilution is made exactly as described 
on page 150 in the preparation of a standard NaOH solution. 
The silver nitrate solution used to determine chlorine in urine 
may be prepared of such a strength that 1 c.c. precipitates just 
10 milligrams of sodium chloride. This is equivalent to 0.006065 
gram of chlorine. A solution of this strength is produced 
when 29.075 grams of pure, fused silver nitrate are dissolved in 
sufficient distilled water to measure one liter of solution. If 
chlorine is to be determined in drinking-water, it is usually nec- 
essary to concentrate the water to at least one-fifth its bulk and 
then to use not more than one or two drops of neutral chromate 
as indicator. The standard silver nitrate for this titration 
should be very dilute. A convenient solution may be prepared 



160 VOLUMETRIC ANALYSIS 

by diluting the standard AgN0 3 for urine i to 10. In saliva 
the sample may be diluted with an equal volume of water and 
titrated the same as in the case of drinking-water. In all quan- 
titative processes where silver chromate is used to determine the 
end point the solution must be practically neutral, as the for- 
mation of this salt is prevented by either acids or alkalis. 

DECINORMAL POTASSIUM SULPHO-CYANATE. 

This solution may be made in a manner similar to that pre- 
viously described for the preparation of standard sodium chlo- 
ride solution, except that a fairly strong solution of ferric alum 
should be used as indicator and the titrated solution should 
contain moderate excess of nitric acid. 

DETERMINATION OF SILVER BY SODIUM CHLORIDE SOLUTION. 

The strength of neutral silver solutions may be determined 
by the use of decinormal sodium chloride using yellow potassium 
chromate as an indicator. It is better to add the silver solution 
from the burette as the precipitate of silver chromate which 
would be formed by adding the indicator to the silver solution 
disintegrates with difficulty. 

DETERMINATION OF SILVER BY POTASSIUM SULPHO-CYANATE 

SOLUTION. 

Silver may be determined volumetrically in nitric acid 
solution by titration with standard KCNS solution, using ferric 
alum as an indicator. The sulphocyanate solution must be 
standardized against decinormal AgN0 3 as follows: Prepare a 
solution containing not less than 10 grams of chemically pure 
KCNS per liter. Place this solution in the burette and put in 
the porcelain dish 10 c.c. of decinormal AgN0 3 which has been 
strongly acidified with nitric acid and fifteen or twenty drops of 



STANDARD SOLUTIONS 

a solution of ferric alum, added as an indicator. The end point 
is indicated by the faint red color of ferric sulphocyanate, pro- 
duced by the first excess of KCNS. The calculation will be the 
same as previously described in the preparation of N/io NaOH 
(page 150). 

DETERMINATION OF CHLORINE LN URINE. 

A rough determination of chlorine may be made by titrating 
10 c.c. of urine with standard silver nitrate, using potassium 
chromate as an indicator (see page 159). An accurate deter- 
mination may be made by acidifying 10 c.c. of urine with nitric 
acid. Add 20 c.c. of decinormal silver nitrate solution and 
titrate the excess of silver nitrate by using standard KCNS with 
ferric alum as an indicator. (In this case the presence of a 
considerable quantity of silver chloride makes it unnecessary, 
and in fact impracticable, to use the silver solution in the bu- 
rette.) Subtract the number of c.c. of N/10 AgN0 3 used for 
this titration from the 20 c.c. at first added and the remainder 
represents the chlorine content of the urine. 

VOLUMETRIC DETERMINATION OF COPPER. 

Into a solution of copper, free from other metals of Group I 
or II, pass H 2 S gas. Wash the resulting copper sulphide thor- 
oughly with H 2 S water, and dissolve in dilute nitric acid; then 
wash the paper in warm water, add to the filtrate (wash water) 
sodium carbonate until precipitate formed is nearly dissolved; 
then add 1 c.c. of dilute NH4OH. Titrate, to complete dis- 
appearance of blue color, with KCN solution previously stand- 
ardized after this same method against pure copper wire. A 
little practice is required in determining the end point to give 
the process any degree of accuracy. An excess of ammonia 
should be avoided, as it interferes with the accuracy of the end 
point. 



162 VOLUMETRIC ANALYSIS 

VOLUMETRIC DETERMINATION OF ZINC. 
(For use in analysis of amalgam alloys.) 

The solution from which silver and copper have been re- 
moved, together with all wash- water, may be concentrated; 
if acid in reaction it should be evaporated to dryness, and the 
residue dissolved in water; then add a fairly strong solution 
of oxalic acid and an equal volume of strong alcohol. Allow 
to stand 15 to 30 minutes, filter, and wash with 70% alcohol till 
oxalic acid is removed, dry until the alcohol has disappeared, 
dissolve in dilute sulphuric acid, and titrate the solution with 
N/10 permanganate and calculate the zinc from the amount 
of oxalic acid found. 

This method is usually fully as satisfactory as the gravi- 
metric determination given on page 165. 

VOLUMETRIC DETERMINATION OF CALCIUM. 

(For use in saliva analysis.) 

This method is based upon that recommended by Dr. Percy 
R. Howe, Dental Cosmos, April, 191 2. To 5 c.c. of saliva, add 
as much more distilled water and a slight excess of oxalic acid 
or ammonium oxalate (5 c.c. of normal solution will be sufficient). 
Add ammonium water to alkaline reaction, heat nearly to the 
boiling point, and allow to stand for twenty to thirty minutes. 
Filter through a hardened filter paper into a small beaker which 
is allowed to stand on a piece of black glazed paper. Under 
these circumstances, a slight rotary motion of the beaker will 
show if any of the white precipitate of calcium oxalate is passing 
through the paper. 

After filtration is complete, wash five times in hot distilled 
water; then place the precipitate, together with the paper, into 
a small beaker, add about 30 c.c. of dilute sulphuric acid, and 
heat nearly to the boiling point; then titrate with N/20 perman- 
ganate solution. 



STANDARD SOLUTIONS 163 

GRAVIMETRIC DETERMINATIONS. 

Gravimetric determinations are, as a rule, more accurate 
than volumetric; but they require greater care and attention 
to details, making them less satisfactory in the hands of the 
beginner. Some determinations, however, on account of diffi- 
culties in obtaining accurate end points and absolute separations, 
are really easier when made by gravimetric processes. A few 
of these will be given. 

GRAVIMETRIC DETERMINATION OF TIN AS Sn0 2 . 

Tin may be separated from dental alloys in the absence of 
gold or platinum by simply dissolving the alloy in nitric acid. 
Tin will remain as a white insoluble me tas tannic acid. " As 
stated on page 40 metastannic acid, upon long standing, will 
change to somewhat soluble compounds, hence this operation 
should be completed with reasonable rapidity. After complete 
disintegration of the alloy, the insoluble tin compound may be 
separated by filtration through asbestos fiber, contained in a 
Gooch crucible. The method of procedure is as follows: 

A little fine asbestos fiber, washed in acid and held in sus- 
pension in water, is placed on the bottom of the crucible. The 
crucible is then placed in the top of a filtering flask from which 
the air is exhausted by the suction pump. This packs the 
asbestos down firmly on the bottom of the crucible in a thin 
layer, and care should be taken that the quantity of asbestos 
used is such that water will pass through it easily. The cruci- 
ble with asbestos is next dried, ignited, and weighed. Now 
transfer the precipitate of tin oxide (metastannic acid) to the 
crucible, taking care that none is lost, and wash thoroughly six 
or eight times, then dry, ignite strongly, and weigh again. 

If the ignited residue, weighed as tin oxide, does not contain 
gold or platinum, the weight of tin may be obtained by multi- 
plying the weight of the ash by 0.788. 



164 VOLUMETRIC ANALYSIS 

GRAVIMETRIC DETERMINATION OF SILVER. 

The gravimetric determination of silver is not difficult, and 
is rather more accurate than the volumetric method. The 
silver is obtained in the form of silver chloride. This is separated 
by nitration through an ashless paper, and dried. Then the 
dried precipitate is removed as completely as possible onto a 
square of black glazed paper and preserved under a funnel or 
bell glass. The filter paper, containing traces of silver chlo- 
ride which could not be removed, is next incinerated in a pre- 
viously weighed porcelain crucible. 

As slight reduction of silver chloride to silver may take place 
during the ignition of the paper, it is necessary to add, after the 
paper is completely burned, a drop or two of nitric acid, and after 
the excess has been driven off by gentle heat, a drop or two of 
hydrochloric acid. This treatment dissolves any reduced silver 
and precipitates silver chloride. After carefully heating to dry 
the precipitate in the crucible, the reserved portion of silver 
chloride is carefully brushed into the crucible, and the whole 
ignited until the silver chloride begins to fuse. It is then cooled 
and weighed as silver chloride. 

GRAVIMETRIC DETERMINATION OF COPPER. 

Copper may be determined quite easily by electrolysis of 
the faintly acid (H 2 S0 4 ) solution. The copper solution must be . 
freed from other metals and preferably be obtained as a solu- 
tion of copper sulphate of approximately o.i of i% of copper. 
50 c.c. of such a solution are put into a platinum dish which 
is placed upon a copper plate connected with the negative pole 
of a battery. A strip of platinum suspended from the positive 
pole is immersed in the solution and the current allowed to pass 
for from three to twelve hours, according to the strength of the 
copper solution. The ordinary no- volt (direct) current em- 
ployed for electric lighting may be used by introducing a re- 



STANDARD SOLUTIONS 165 

sistance of from three to six 40 watt lamps. After the copper has 
been entirely deposited the residual solution is drained out of the 
platinum dish, a little alcohol added, which is also drained out, 
and by setting fire to the last traces of alcohol the precipitated 
copper is dried and in condition to weigh. Care must be taken 
to avoid oxidation of the finely-divided copper; if it turns black 
too much heat has been used and partial oxidation has taken 
place, which has, of course, resulted in an increase of weight. 

GRAVIMETRIC DETERMINATION OF ZINC. 

Zinc may be determined gravimetrically by precipitation as 
zinc sulphide as follows: To a measured portion of the solution, 
free from all metals (except zinc) of Groups I, II, III, and IV, 
add ammonium chloride, ammonium hydroxide, and ammonium 
sulphide, as in qualitative analysis. Filter the precipitated 
zinc sulphide on to counterpoised filters, wash thoroughly with 
water containing a little ammonium sulphide, dry in an atmos- 
phere free from oxygen (hydrogen or hydrogen sulphide), and 
weigh as zinc sulphide. 

Gravimetric Assay of Gold and Silver in the Dry Way. 

It is often more convenient to determine gold and silver by 
the fire assay than by the volumetric methods previously given. 
This is accomplished usually by fusion with an excess of lead 
and a borax flux. The mixture is kept at a high heat for up- 
wards of thirty minutes, with a current of air passing over the 
surface of the molten metals. This serves to oxidize and carry 
away the baser metals, leaving the gold and silver with but a 
slight amount of lead, possibly a trace of copper and tin. The 
purification is completed by cupellation. When the traces of 
lead and other metals are absorbed by the cupel or are driven 
off as volatile oxides, the button of gold and silver is next cooled 
very slowly and carefully weighed. From this the silver may be 
dissolved by nitric acid unless the gold is in considerable excess, 



166 VOLUMETRIC ANALYSIS 

which would rarely be the case. If it happens that the gold 
is present in sufficient quantity to prevent the solution of the 
silver in nitric acid a known weight of pure silver may be added 
in amount sufficient to increase the percentage of silver to 
seventy-five or over, fused, and then all the silver dissolved out 
with nitric acid, leaving the gold. 

The gold which has resisted solution may be found as small 
black particles or grains in the bottom of the crucible. This 
should be carefully washed with distilled water by decantation, 
very carefully dried and brought to a red heat, which will give 
a button of pure gold. This may be weighed and the weight 
subtracted from the weight of gold and silver button previously 
obtained. 

QUANTITATIVE ANALYSIS OF DENTAL ALLOYS 
CONTAINING Au, Sn, Ag, Cu, Zn. 

Weigh accurately 0.5 gram of alloy which has been reduced 
to fine filings and from which all particles of iron have been 
carefully removed by a magnet, transfer to a beaker, and dis- 
solve in 15 c.c. of strong HN0 3 and 10 c.c. of H 2 by aid of 
gentle heat. If the sample contains tin or gold, complete solu- 
tion will not be effected, but, by watching the character of the 
sediment through the bottom of the beaker, it is possible easily 
to determine when the alloy has been completely disintegrated. 

If silver is to be determined by titration with NaCl and 
K 2 Cr0 4 , evaporate on a water-bath till all nitric acid has been 
expelled. 

If silver is to be determined by the sulphocyanate solution, 
evaporation at this point is not necessary. In either case, make 
the whole solution up to 250 c.c. with distilled water; then filter 
out tin and gold, following the method given under gravimetric 
determination of tin (page 163), reserving the filtrate before any 
wash- water has been added. For convenience this filtrate may be 
marked "A." Titrate this filtrate (" A") for silver as follows: 



STANDARD SOLUTIONS 167 

Take a measured volume, about 30 c.c., and place in a por- 
celain dish with ferric alum as indicator. 

Then place the standard KCyS in the burette and titrate 
till the faint red color is produced. 

Suppose 8 c.c. of KCyS is used. The weight of silver in 1 c.c. 
of a decinormal solution is 0.0108 gram. Multiplying 8 by 
0.0108 = 0.0864. Divide by number of c.c. of solution taken, 
0.0864 -T- 30 = 0.00288 gram Ag in 1 c.c. of solution. 

Multiply by whole number of cubic centimeters and divide 
by weight of alloy taken and result will be percentage of silver. 

Take 100 c.c. of filtrate " A " and precipitate silver by slight 
excess of HC1. Filter and wash precipitate thoroughly with 
warm water. Concentrate filtrate and wash-water, which may 
be designated as filtrate " B." Pass H 2 S gas into "B" till 
copper is entirely separated as CuS. Filter and wash CuS 
seven or eight times with dilute H 2 S water. Reserve filtrate 
and wash-water as filtrate " C." Dissolve CuS in dilute HN0 3 , 
wash paper carefully, concentrate, and determine amount of 
copper by deposition upon platinum (page 164). Concentrate 
filtrate " C " and determine zinc by volumetric method given on 
page 162. Gold and tin in residue insoluble in nitric acid may 
be determined by method given on pages 163 and 158. 

QUESTIONS IN VOLUMETRIC WORK. 

Why is an N/10 solution of hydrochloric acid more generally 
serviceable than a similar solution of oxalic acid? 

Why use nitric acid for titration of chlorine in urine by use 
ofKCNS? 



PART IV. 

MICROCHEMICAL ANALYSIS, 

CHAPTER XVIII. 

METHODS. 

The advantages of microchemistry are many, as claimed by 
its enthusiastic advocates, and there are two particulars in which 
these methods strongly recommend themselves to the dental 
practitioner: (i) Microchemical analysis deals with exceedingly 
minute portions of matter, making the examination of very 
small particles of substance easily possible. (2) Three or four 
one-ounce " drop-bottles " and a few two-drachm vials will 
contain all necessary reagents, and in consequence three feet 
of bench-room will furnish ample laboratory space. 

The principles of microchemical analysis are, of course, the 
same as for any analysis, but the processes employed are quite 
different and need some explanation. In microchemical analysis 
the production of crystals of characteristic form furnishes per- 
haps the most rapid method of detection of an unknown sub- 
stance, and in this we are greatly aided by the use of polarized 
light, which not only helps in the differentiation of crystals but 
often makes it possible to see and distinguish small or trans- 
parent crystals which might otherwise escape notice altogether. 

Use of Microscope. — For the examination of the crystals 
mentioned in this chapter, also for the work required on saliva 
or urine, lenses of comparatively low power are sufficient. For 
most of the microchemical tests, a No. 3 Leitz or a 16-mm. Bausch 
& Lomb objective will be found satisfactory. For a few micro- 

168 



METHODS 169 

chemical tests and for urine, an 8-mm. Bausch & Lomb or a 
No. 5 Leitz objective will give better results in the hands of a 
beginner than one of higher power. 

In using the microscope for microchemistry, the preparation 
should always be covered with a cover glass and the examination 
be made with the low-power lens if possible. The object in 
covering is to prevent any action by reagent upon the objective. 
As a further precaution, it is well to form the habit of first 
lowering the objective and then focusing by upward movement 
of the draw- tube. 

Formation of crystals may be brought about in two ways: 
first, by precipitating insoluble crystalline salts by use of re- 
agents, as in ordinary qualitative analysis; second, by allowing 
salts to crystallize by spontaneous evaporation of the solvent. 

If the first method is to be employed it is essential to have 
the dilution fairly constant in order to obtain crystals which shall 
be comparable with those obtained at other times or by other 
individuals. The tendency of strong solutions is to give amor- 
phous precipitates. Sometimes the precipitate will be amor- 
phous when first thrown down, but upon standing will assume 
crystalline form. To secure the uniformity of results necessary 
to correct deductions, the following method of procedure should 
be exactly followed every time. 

The reagent should be of uniform strength, usually one or 
two per cent. Place on a clean microscope-slide a small drop of 
the solution to be tested, and as close as possible without touching 
it, one of about equal size of the reagent to be used. Now bring 
the drops together by tapping the slide or with a small glass rod. 
If a precipitate forms immediately, cover with a cover-glass (this 
must always be done) and examine with the microscope. If the 
precipitate is crystalline, note the form, and in any case, whether 
crystalline or not, repeat the test after diluting the unknown 
solution one-half. If the second test gives an amorphous pre- 
cipitate, or crystals of different shape from the first, continue 



170 MICROCHEMICAL ANALYSIS 

the dilution of the unknown till a point is reached when admixture 
with the drop of reagent gives no immediate precipitate, but one 
appearing in a few seconds' time (five to thirty). In this way 
we have produced the precipitate under standard conditions or 
as nearly such as is possible with unknown solutions. 

Until thoroughly familiar with the forms obtained by drying 
the various reagents, it is well to evaporate a small drop of the 
reagent alone, on the same slide on which a test is made, for the 
sake of subsequent comparisons. 

Filtration in microchemical examinations, when perhaps only 
a few drops of solution are to be had, may be effected in a very 
satisfactory manner and without appreciable loss by absorption 
as follows: 

Cut a filter-paper about 1 cm. wide and 6 cm. long, double 
it and crease the middle so that it assumes the shape of an in- 
verted V. Put the solution to be filtered in a small watch- 
glass placed at a slight elevation above a microscope slide; 
now place one " leg " of the strip of filter-paper in the watch- 
glass, allowing the end of the other to touch the slide. By capil- 
lary attraction the clear solution will follow over the bend 
in the strip of paper and a drop or two of perfectly clear filtrate 
suitable for the test will be found upon the slide. 

Evaporation of a solution is best effected on a small watch- 
glass held in the fingers and moved back and forth over a low 
Bunsen flame, or else placed over a water-bath. 

The purpose of the microchemical tests here outlined is not 
so much a method of general qualitative analysis, to which they 
are not suited, as it is a specific application of well-known reac- 
tions to concrete examination of substances, the uses and prob- 
able composition of which are known. The details of the various 
tests will be given under classification furnished by the sub- 
stances investigated. 

Our study may include alloys and amalgams, teeth, tartar, 
dental anesthetics, cement, mouth-washes, antiseptics, disin- 



PLATE II. — MICROCHEMICAL ANALYSIS. 




Fig. i. 
Calcium Oxalate. 




Fig. 3. 
Strontium Oxalate. 





Fig. 2. 
Cadmium Oxalate. 




Fig. 4. 
Sodium Oxalate (P.L.). 




Fig. 5. 
Oxalate of Urea. 



Fig. 6. 
Zinc Oxalate. 



PLATE III. — MICROCHEMICAL ANALYSIS. 





Fig. i. 
Ammonium Platinic Chloride. 



Fig. 2. 
Eucaine and Platinic Chloride. 




Fig. 3. 
Potassium Platinic Chloride. 





Fig. 4. 
Cocaine and Potassium Permanganate, 




Fig. 5. 
Tri-brom-phenol. 



Fig. 6. 
Morphine. 



METHODS 171 

fectants, and sediments obtained from the saliva and from the 
urine. 

The following crystals are selected as among those most 
frequently met with in the analysis of the above substances or 
best suited for the study of microchemical processes, and the 
student should make each test here indicated and carefully draw 
the crystals produced: 

1. Calcium oxalate from 2% H 2 C 2 4 and CaCl 2 solutions 
(Plate II, Fig. 1). 

2. Cadmium oxalate from 2% H 2 C 2 4 and CdS0 4 solutions 
(Plate II, Fig. 2). 

3. Strontium oxalate from 2% H 2 C 2 4 and Sr(N0 3 ) 2 solutions 
(Plate II, Fig. 3). 

4. Sodium oxalate by evaporation of aqueous solution, also 
by evaporation of urine containing Na 2 C 2 4 (polarized light) 
(Plate II, Fig. 4). 

5. Urea oxalate from 2% H 2 C 2 4 and urea solution (Plate 

n, Fig. s). 

6. Ammonium-magnesium-phosphate from magnesium mix- 
ture * and sodium phosphate (Plate IV, Fig. 2). 

7. Ammonium platinic chloride (Plate III, Fig. 1). For 
preparation of crystals see pages 46 and 47. 

8. Potassium platinic chloride, H 2 PtCl 6 (Plate III, Fig. 3). 
For preparation of crystals see page 47. 

9. Sodium urate by evaporation (polarized light) (Plate X, 
Fig. 3, opp. page 255). 

10. Crystals formed from cocaine and potassium perman- 
ganate (Plate III, Fig. 4). 

11. Crystals formed from phenol and dilute bromine water 
(tribromphenol) (Plate III, Fig. 5). 

12. Crystals formed from morphine solutions and ammonia 
(morphia) (Plate III, Fig. 6). 

* Magnesium mixture as used in urine analysis to precipitate phosphates 
contains MgCl 2 (or MgS0 4 ), NH 4 C1, and NH 4 OH. 



172 MICROCHEMICAL ANALYSIS 

13. Crystals formed from morphine and Marine's reagent 
(Plate IV, Fig. 1). 

14. Platinum chloride and /3-eucaine (Plate III, Fig. 2). . 

15. Stovaine and platinum chloride (Plate IV, Fig. 4.). 

16. Alypin and KI (Plate IV, Fig. 6). 

The list may be extended to include the crystals produced 
by various alkaloidal salts with the common reagents, also sub- 
stances usually employed in the manufacture of the various 
dental preparations. 



PLATE IV.— MICR0CHEM1CAL ANALYSIS. 




Fig. i. 
Morphine and Marine's Reagent. 




Fig. 3- 
Cocain with Tin Chloride. 





Fig. 2. 
Magnesium Ammonium Phosphate. 




Fig. 4. 

Stovaine and Platinic Chloride, 




Fig. 5- 

Palmitic Acid. 



Fig. 6. 

Alypin and Potassium Iodide. 



CHAPTER XIX. 

LOCAL ANESTHETICS AND ANTISEPTICS. 

(Also some other substances commonly used in dental preparations.) 

In considering the chemistry of local anesthetics we may 
divide them into two classes as follows: 

First, those of definite or well-known composition, and 

Second, preparations of a proprietary nature, the compo- 
sition of which is always problematical. 

In the first class will be found cocaine, eucaine, tropacocaine, 
acoin, ethyl chloride, etc., which will be later alphabetically 
considered. The second class contains a large number of prep- 
arations of all degrees of value, among them some of exceeding 
merit and largely used, others of doubtful worth, some worth- 
less if not dangerous. Many of the preparations of this class 
contain cocaine as the anesthetic, and frequently a little nitro- 
glycerin as a cardiac stimulant to counteract the depressant 
effect of the alkaloid. Carbolic acid and oil of cloves are also 
frequently used. 

Many of the constituents of this class of anesthetics may 
readily be identified. by the processes of microchemical analysis 
to which previous reference has been made; others may be de- 
tected by special tests, some of which are given under the various 
substances in the following list. This list has been extended 
to include a considerable number of preparations of common 
occurrence. 

Acoin, a synthetic compound, chemically diparanisyl-mono- 

/ / (NC 6 H 4 OCH 3 )2 \ \ 
phenetyl-guanidine hydrochloride jC HCll 

\ X (NGH4OC0H5) ' / 



173 



174 MICROCHEMICAL ANALYSIS 

soluble in both alcohol and water. Strongly antiseptic and a 
valuable anesthetic, especially in conjunction with cocaine. 
Acoin should be used only in solution and this should be kept 
in a dark place. 

Adrenalin, a valuable hemostatic and frequently used in con- 
junction with dental anesthetics, is the active principle of the 
suprarenal gland or capsule. It occurs as very small white 
crystals which are not very stable and only slightly soluble 
in water, hence the article is usually sold in solution with sodium 
chloride, according to the following formula taken from a com- 
mercial sample: 

Adrenalin chloride, i part; normal sodium chloride solution 
(with 0.5% chloretone), 1000 parts. This solution is usually 
diluted with the normal (0.6%) salt solution. According to the 
Druggists' Circular, preparations similar to the above are also 
marketed under the names of adrenol, adnephrin, hemostatin, 
suprarenalin (Armour & Co.), suprarenin, etc., see Epinephrine. 

Alypin. — Benzoyl - dimethylamino - methyl-dime thylamino- 
butane hydrochloride, white crystalline, hygroscopic, melts at 
169 C. Soluble in water and alcohol. 

Alypin can be sterilized without decomposition, is not half 
so poisonous as cocaine and is cheaper. Is used in 2% solution. 
Solution should be freshly made and prolonged boiling avoided. 
Sometimes used with adrenalin. (Cosmos, 1908, p. 889.) 

Alypin nitrate occurs as a white, crystalline powder melting 
at 1 59 C, readily soluble in ether. Mfrs.: Farbenfabriken of 
Elberfeld, Elberfeld (Germany) and New York. (Mod. Mat. 
Med., page 21.) 

Test. — Alypin gives needle-shaped crystals with potassium 
iodide, easily produced. (Plate IV, Fig. 6.) 

Ammonium Bifluoride is strongly recommended as a solvent 
for tartar by Dr. Joseph Head of Philadelphia. In Items of 
Interest, Vol. 31, page 174, Dr. Head gives the following method 
for its preparation. Hydrofluoric acid is neutralized with am- 



LOCAL ANESTHETICS AND ANTISEPTICS 175 

monium carbonate, the solution filtered and evaporated to half 
its bulk, the original volume restored by adding more hydro- 
fluoric acid and then the resulting mixture is again concentrated 
to half its volume by evaporation. 

Anesthol, or Anaesthol, is a mixture of ethyl chloride and 
methyl chloride, used as a local dental anesthetic. The name is 
also applied to a general anesthetic given by inhalation and con- 
sisting of a mixture of ethyl chloride 17 parts, chloroform 35.89 
parts, and ether 47.1 parts. 

Anaestheaine, a local anesthetic, contains five grains of 
stovaine to the fluid ounce. 

Argyrol, a protein compound of silver, occurs as dark brown 
crystals containing 30% of silver. It is easily soluble in water. 
It does not precipitate chlorine nor coagulate albumin, and is 
recommended for use in place of ordinary silver nitrate. 

Aristol is given by the U. S. D. as a synonym for dithymol- 
diiodide which contains 45% of iodine and is used as an anti- 
septic similarly to iodoform. 

Atropine, an alkaloid obtained from belladonna, usually used 
combined with sulphuric acid, (CnH^NOs^H^SC^; the alkaloid 
is only sparingly soluble in water but the sulphate is easily sol- 
uble, dissolving in about one-half part of water at ordinary tem- 
perature. A one per cent, solution is said to produce complete 
insensibility of the nerves in cases in which an artificial tooth is 
inserted in a living root. (U. S. D., page 249.) 

Tests. — Atropine may be separated from a local anesthetic 
by first rendering the mixture alkaline with ammonia and shaking 
with chloroform. Upon evaporation of the chloroform solution 
on a watch-glass the resulting residue may be tested by adding 
a drop or two of sulphuric acid and a trace of potassium bichro- 
mate and a little water. The odor of bitter almonds is produced. 
A more conclusive test is to convert the alkaloid, which has 
been dissolved by the chloroform, into a salt by the addition of a 
few drops of acetic acid, evaporating to complete dryness, taking 



176 MICROCHEMICAL ANALYSIS 

up in a few drops of distilled water and placing one or two drops 
of this solution in the eye of a cat, when, if atropine is present, a 
dilation of the pupil occurs in from fifteen minutes to. an hour 
and a half, according to amount present. 

Borax. — Sodium tetraborate, Na 2 B 4 7 , is used in antiseptic 
solutions and may be detected as follows: evaporate a little of 
the solution to dryness, add a little HC1, evaporate to dryness 
a second time, then add a very dilute HC1 solution containing 
tincture turmeric. Upon drying this mixture a beautiful pink 
color appears. If much organic matter is present it may be 
burned off in the Bunsen flame before the addition of any 
acid. 

Carbolic Acid. — See Phenol. 

Chloral Hydrate, CCI3CHO.H2O, a crystalline solid com- 
posed of trichloraldehyde, or chloral, with one molecule of water 
(U. S. P.), easily soluble in water, may become with alcohol a 
chloral alcoholate comparatively insoluble in water. 

Tests. — Chloral may be detected by adding to the sus- 
pected mixture a few cubic centimeters of fairly strong alco- 
holic solution of KOH or NaOH with one drop of aniline oil and 
heating, when isobenzonitril is produced, which has a peculiarly 
disagreeable and characteristic odor. This test is also given 
by chloroform, which is produced by heating chloral hydrate 
with caustic alkali. If more than traces of chloral are present 
this latter reaction may be a sufficient test. 

Chloretone, CCl3COH(CH 3 ) 2 , is the commercial name of 
acetone-chloroform or tertiary trichlorbutyl alcohol. Made 
from chloroform, acetone, and an alkali, and occurs as small 
white crystals, with taste and odor like camphor. It is dissolved 
by alcohol and glycerol and to a slight extent by water. 

Chloroform, trichlormethane, CHCI3, prepared by action of 
chlorinated lime on acetone. Chloroform is a heavy colorless 
liquid with a specific gravity of 1.490 at 15 C. Is very volatile 
and used as a solvent for gutta-percha, caoutchouc, many 



LOCAL ANESTHETICS AND ANTISEPTICS 177 

vegetable balsams, camphor, iodine, bromine, and chlorine; 
it also dissolves sulphur and phosphorus to a limited extent. 

Tests. — It may be detected by its odor, when heated, or by 
the isobenzonitril test to which reference has been made under 
chloral hydrate. 

Cocaine is the alkaloid obtained from erythroxylon coca. 
The hydrochlorate, Ci7H 21 N0 4 HCl, is the salt most usually 
employed. This is easily soluble in water and very largely 
used as a dental anesthetic in a one or two per cent, solution. 

Tests. — Cocaine solutions respond to the usual alkaloidal 
reagents. With 1% solution potassium permanganate gives 
pink plates resembling cholesterol (Plate III, Fig. 4) in form 
but not in color. 

Dilute cocaine solution with picric acid gives a yellow pre- 
cipitate which becomes crystalline on standing. Quite char- 
acteristic crystals may also be obtained from dilute cocaine 
solutions and stannous chloride in the presence of free HC1. 

Creosote. — A mixture of phenols derived from the destruc- 
tive distillation of wood tar. It is a heavy oily liquid acting 
when pure as an escharotic. It is analogous in many respects 
to carbolic acid and may be used for similar purposes. To 
distinguish between creosote and carbolic acid, boil with nitric 
acid until red fumes are no longer given off. Carbolic acid will 
give yellow crystalline deposit; creosote will not. An alco- 
holic solution of creosote is colored emerald green by an alcoholic 
solution of ferric chloride. Phenol is colored blue. 

Cresol is the next higher homologue to phenol, having a 
formula C 6 H 4 CH 3 OH, boiling at 198 C. It is largely used, 
usually together with allied compounds from coal-tar, as anti- 
septic and disinfectant solutions. 

Ektogan. — Peroxide of zinc, Zn0 2 , designed for external 
use. 

Epinephrine. — The active principle is the suprarenal 
glands. Chemically it is an 0-dihydroxyphenyl-ethanolmethyl- 



17& MICROCHEMICAL ANALYSIS 

amine, C 6 H3(OH)2.CHOH.CH 2 NHCH 3 . This is a weak base 
which combines with hydrochloric acid to form the hydrochlo- 
ride in which form it is usually used in dilutions of one part to a 
thousand. It acts as a cardiac stimulant causing rise in blood 
pressure with slower heart action, acting somewhat in the same 
way as digitalis. 

Ethyl Chloride, monochlorethane, C 2 H 5 C1. This is a gaseous 
substance at ordinary temperature, but when used as a dental 
anesthetic it is compressed to a colorless liquid which has a 
specific gravity of 0.918 at 8° C, is highly inflammable and usu- 
ally sold in sealed glass tubes of from ten to thirty grams 
each. 

p-Eucaine is the hydrochlorate of bezoylvinyldiacetone- 
alkamine, and occurs as a white, neutral powder, soluble in 
about thirty parts of cold water. It is used like cocaine as a local 
anesthetic, and is claimed to be less toxic, and sterilizable by 
boiling without danger of decomposition. It is usually applied 
in from one to five per cent, solutions, which are conveniently 
prepared in a test-tube with boiling water. It is also marketed 
in the form of i^-and 5-grain tablets. (Druggists' Circular.) 

Test. — /3-Eucaine gives characteristic crystals with platinic 
chloride. (Plate III, Fig. 2.) 

Eucain Lactate. — " Eucain lactate is used in two to five per 
cent, solution as a local anesthetic in ophthalmic and dental prac- 
tice and in ten to fifteen per cent, solution when used in the nose 
or ear." (Review of American Chemical Research, page 97, 

1905O 

Eudrenin is a local anesthetic marketed in capsules of 
0.5 c.c. containing 1/12 grain of eucain and 1/4000 grain of 
adrenalin hydrochloride. It is used as a local anesthetic, 
chiefly in dentistry. The contents of one or two capsules, ac- 
cording to the number of teeth to be extracted, are injected into 
the gums ten minutes before extraction. Mfrs. : Parke, Davis & 
Co., Detroit, Mich. (Mod. Mat. Med., page 147.) 



LOCAL ANESTHETICS AND ANTISEPTICS 179 

Eugenol, C10H12O2, synthetical oil of cloves. Eugenol is mis- 
cible with alcohol in all proportions. Exposure to air thickens 
and darkens it. Should be kept in well-stoppered amber-colored 
bottles (U. S. D.). 

Europhen — recommended by Dr. J. P. Buckley as a sub- 
stitute for iodoform (Dental Review, Vol. 21, page 1284). 

Di-iso-butyl-cresol is described as a bulky yellow powder of 
faint saffron odor and containing 28% of iodine. (Mod. Mat. 
Med., page 152.) 

Formaline, Formol, Formine, etc., are commercial names for 
a 40% aqueous solution of formaldehyde, HCHO, prepared 
by the partial oxidation of methyl alcohol. Formaline is a power- 
ful disinfectant very generally used. (For test see page 386, 
Exp. 83.) 

Glycerol is a triatomic alcohol, C 3 H 5 (OH) 3 , a colorless liquid 
of syrupy consistence and sweetish taste, specific gravity 1.250 
at 1 5 C. It is easily soluble in either water or alcohol. 

Tests. — Upon heating with acid potassium sulphate (solid) 
it is decomposed, giving off odor of acrolein, which is usually 
sufficient for its identification. A further test may be made by 
moistening a borax bead on a platinum wire with the suspected 
solution (after concentration) and holding in a non-luminous 
flame, to which it will give a deep-green color which does not 
persist. Glycerol when present is apt to interfere with charac- 
teristic crystallization of many precipitates. 

Gram's Solution, Kuhne's modification, contains two grams 
of iodine, and four grams potassium iodide in 100 c.c. of water. 

Gutta-percha. — The name signifies scraps of gum. It is ob- 
tained as a milky exudate from a number of tropical trees. It 
is soluble in ether, chloroform, carbon disulphide, toluene, and 
petroleum ether. It may be freed from impurities by shaking 
the solution with calcium sulphate, which will mechanically carry 
coloring matter and other impurities with it as it slowly settles 
out from the mixture. It is not soluble in alcohol or in water. 



l8o MICROCHEMICAL ANALYSIS 

Heroin is a diacetic ester of morphine. It is usually ob- 
tained as the hydrochloride and occurs as a white powder, solu- 
ble in two parts of water. Its action is similar to that of mor- 
phine; it answers to the usual color tests for morphine, but may 
be distinguished from it by the fact that it will yield acetic ether 
upon heating with alcohol and sulphuric acid. 

Hopogan (also known as biogen) is a peroxide of magnesium, 
Mg0 2 , recommended as a non-poisonous and non-astringent 
intestinal germicide. 

Hydrogen Peroxide, or dioxide, H 2 2 , is, when pure, a syrupy 
liquid without odor or color. It is sold under various trade 
names in aqueous solution containing about 3% and yielding 
upon decomposition about 10 volumes of oxygen gas. It is 
used also as an escharotic in etherial solutions containing twenty- 
five to fifty per cent. H2O2. Peroxide solutions may be concen- 
trated by heat without decomposition if kept perfectly free from 
dirt or traces of organic matter. It is readily prepared by treat- 
ment of metallic peroxides, as Ba0 2 with dilute acids. 

Ba0 2 + H 2 S0 4 = BaS0 4 + H 2 2 
or Ba0 2 + H 2 + C0 2 = BaC0 3 + H 2 2 . 

This latter reaction has the advantage of producing an insolu- 
ble barium compound and at the same time introducing no 
objectionable acid. The peroxides of sodium, calcium, magne- 
sium, and zinc may also be used; Zn0 2 , however, is compara- 
tively expensive and used in powder form as an antiseptic 
dressing rather than as a source of H 2 2 . Na 2 2 is valuable as 
a bleaching agent, because for this purpose an alkaline solution 
is required and the solution of Na 2 2 in water produces both 
alkali and H 2 2 according to the following reaction: 

Na 2 2 + 2 H 2 = 2 NaOH + H 2 2 . 

Sodium perborate (page 185), also sold as euzone, is a powder 
which will produce H 2 2 in water. Commercial H 2 2 solutions 



LOCAL ANESTHETICS AND ANTISEPTICS 181 

are usually acid in reaction, as such solutions are more stable 
than if neutral or alkaline. 

Test. — Add to a solution of H 2 2 a few drops of bichromate 
of potassium solution and a little dilute H 2 S0 4 . Shake cold with 
a little ether in a test-tube. The ether should be colored blue. 
(For further tests see experiments.) 

LugoPs Caustic Iodine is made of iodine and potassium iodide, 
one part of each dissolved in two parts of water. 

Lugol's Iodine Solution. — See appendix under Iodine Solu- 
tion. 

Menthol is the stearopten obtained from the oil of pepper- 
mint. It is a volatile crystalline substance having a formula 
C 6 H 9 OHCH3C3H 7 . Menthol is but slightly soluble in water 
but freely soluble in alcohol, ether, chloroform, or glacial acetic 
acid. The presence of menthol may usually be detected by its 
odor. If the odor should be suggestive but not distinctive 
it is well to place a little of the substance on a filter-paper, rub 
it between the thumb and finger, thereby obtaining a " fractional 
evaporation," when the more easily volatile substance will pass 
off first, thus producing a partial separation of substances. 

Mercuric Chloride, corrosive sublimate, HgCl 2 , is soluble in 
about sixteen parts of water and three parts of alcohol. It is a 
powerful antiseptic, in aqueous solution i/iooo to 1/5000, but 
should never be used in mouth- washes. 

Tests. — A drop of the suspected solution with a trace of 
potassium iodide will give a red precipitate of mercuric iodide 
soluble in excess of either reagent. With lime-water or fixed 
alkaline hydroxides a black precipitate is produced. A drop of 
mercurial solution placed on a bright copper plate will leave 
a tarnished spot due to the reduction of the mercuric salt and 
subsequent amalgamation of the metal. 

Methethyl. — Ethyl chloride mixed with a little methyl 
chloride and chloroform is said to be the composition of a local 
anesthetic sold under the name of methethyl (U. S. D.). 



l82 MICROCHEMICAL ANALYSIS 

Methyl Chloride, CH 3 C1, is a colorless gas which condenses to 
a liquid at 23 C. Methyl chloride is easily soluble in alcohol, 
somewhat in water, and is used in a similar manner to ethyl 
chloride. 

Morphine, C17H19NO3, alkaloid from opium. Solutions for 
use are made from the sulphate, hydrochlorate, or acetate. The 
alkaloid itself is insoluble in water; its salts are easily soluble. 

Morphine may be separated from solutions containing it by 
making the solution alkaline with ammonia, and shaking out 
the precipitated alkaloid with warm ethyl acetate. Upon 
evaporation of the solvent the residue may be tested with 
Frohde's reagent (sodium molybdate, 1%, in strong sulphuric 
acid). The color obtained should be a violet, changing usually 
to brown; a pure blue color is not distinctive for morphine. If 
the morphine solution is of sufficient strength the addition of am- 
monia will produce minute crystals of the alkaloid as shown on 
Plate III, Fig. 6. Dental anesthetics containing morphine will 
give precipitates with the usual alkaloidal reagents. Marine's 
reagent (Cdl 2 ) gives crystals represented on Plate IV, Fig. 1. 

Nirvanin, hydrochloride of diethyl-glycocoll-^-amino-o-oxy- 
benzoic-methylester, of the formula 

(CH 2 N) = (C 2 H 5 ) 2 HC1 
I 
CO.NH.C 6 H 3 (OH)COOCH 3 . 

White prisms soluble in water and in alcohol, melt at 185 C, 
violet reaction with ferric chloride. 

Nitroglycerin, C 3 H 5 (N0 3 )3, is used as a cardiac stimulant 
in alcoholic solution, the U. S. P. Spiritus Glonoini, containing 
1% by weight of the substance. 

Test. — Extract the dry substance, or the evaporated residue, 
with alcohol. Filter and evaporate to dryness. Add 1 c.c. of 
sulphuric acid and 1 c.c. of phenoldisulphonic acid. Heat over 
a water bath for five minutes; add water and excess of ammonia. 



LOCAL ANESTHETICS AND ANTISEPTICS 183 

A deep yellow color of ammonium picrate indicates nitrates in 
the original substance. Exp. No. 148, p. 397. 

Novocaine, discovered by Uhlf elder and Einhorn, is a hydro- 
chloride ^-aminobenzoyl-diethylamino-ethanol. It occurs as 
thin colorless needles; melts at 15 6° C, soluble in one part water 
and thirty parts alcohol. It is seven times less toxic than cocaine, 
and three times less toxic than stovaine. It can be sterilized by 
boiling, and is used in 1/2 to 2% solution often with adrenalin 
1/1000. (Mod. Mat. Med., page 275.) 

Novocaine, if intended to represent a solution which is iso- 
tonic with the blood corpuscles, must be dissolved in a 0.92 
per cent, sodium chloride solution. (Dental Cosmos, 19 10, page 
605.) 

Oil of Cloves, oil of Gaultheria, and other essential oils may 
be detected by the same process of fractional evaporation as 
suggested for menthol. In testing for the presence of any sub- 
stance by its odor, it is usually necessary to make a comparative 
test on known samples using the same methods. 

Orthoform, C 6 H 3 OH(NH2)COOCH 3 , methylpara-amino-meta- 
oxybenzoate, used as an anesthetic and antiseptic, is without 
odor, color, or taste, is slightly soluble in water, and easily soluble 
in alcohol or ether. 

Phenol. — Carbolic acid, C 6 H 5 OH, obtained from the de- 
structive distillation of coal-tar. A light oily liquid of specific 
gravity of 0.94-0.99. Carbolic acid is usually obtained as a 
white crystalline mass soluble in twenty parts of water. The 
pure acid turns pink with age, but does not suffer deterioration on 
account of this change of color. The addition of from five to 
eight per cent, of water will cause liquefaction of the crystals and 
the preparation becomes permanently liquid. It is easily soluble 
in glycerol and strong solutions may thus be prepared. Car- 
bolic acid is sometimes added to local, anesthetics with the in- 
tent of rendering the solution sterile, but as shown by Dr. 
Endelman (Dental Cosmos, Vol. 45, page 44) it would be neces- 



184 MICROCHEMICAL ANALYSIS 

sary, in order to prevent the development of micro-organisms, to 
add the acid in proportion that would render the solution unfit 
for hypodermic purposes. ^ 

Tests. — Phenol may be detected in the majority of prepara- 
tions by the addition of bromine-water, which gives white crys- 
tals of tribromphenol (see Plate III, Fig. 5). See also Exp. 145. 

Phenol Compound. — Dr. Buckley's formula for treatment of 
root canals — menthol 1.3 grams-, thymol 2.6 grams, and phenol 
12 c.c. 

Potassium Hydroxide, KOH, gives an alkaline reaction to 
litmus paper and may be detected by the ordinary methods of 
inorganic analysis. 

Rhigolene is a light inflammable liquid obtained from petro- 
leum, boiling at about 18 C, used as a spray for the production 
of low temperature, similarly to methyl or ethyl chloride. It 
is readily inflammable and the vapor, mixed with certain pro- 
portions of air, is explosive. It should be kept in a cool place. 

Ringer's Solution, which is used as a solvent for Novocaine 
and other anesthetics has the formula: 

Sodium Chloride 0.50 

Calcium Chloride 0.04 

Potassium Chloride 0.02 

Distilled water 100.00 

Saccharin. — Saccharin is official in the ninth revision of the 
Pharmacopoeia as benzosulphinidum. It is a derivative of 
toluene having a formula of C6H4COSO2NH, being benzoyl- 
sulphonimide. It is a white crystalline powder melting at 219 
to 222° C. 

It is said to be at least three hundred times sweeter than 
cane sugar and is used in mouth- washes, tooth-paste, etc., as a 
flavor and an antiseptic. 

Test. — Add a few drops of potassium hydroxide solution 
to a little saccharin; heat for a few minutes. Acidify with 



LOCAL ANESTHETICS AND ANTISEPTICS 185 

hydrochloric acid; add a few drops of ferric chloride; when a 
reddish brown or purplish color is produced. 

Silver Nitrate, AgN0 3 , crystallizes in colorless plates without 
water of crystallization; used as an antiseptic, disinfectant, or 
escharotic. It is freely soluble in water and may be detected by 
the ordinary methods of qualitative analysis (page 20) . 

Sodium Chloride, NaCl, is a constituent of many prepara- 
tions designed to be used hypodermically. Experience has 
proved the value of such addition; perhaps the reason for its 
desirability is given by Dr. G. Mahe, of Paris, in the Dental 
Cosmos for September, 1903, in the statement that sodium 
chloride added in excess to a toxic substance diminishes its 
toxicity by one-half, and this has been demonstrated particu- 
larly with cocaine. 

Sodium Perborate, a powder having the composition 
NaB034 H 2 0, which will furnish 10% of available oxygen and 
produce H 2 2 with water; very stable and recommended as a 
bleach-powder. 

Sodium perborate may be made by- thoroughly mixing 
sodium peroxide (Na 2 2 ) with crystallized boric acid and stir- 
ring the mixture gradually into cold water. The proportions 
recommended by V. E. Miegeville in the Dental Cosmos for 
1905, page 1 38 1, are 78 grams of the sodium peroxide, 248 grams 
of the boric acid, and two liters of water. The sodium perborate 
is formed spontaneously and separates from the solution as a 
white crystalline powder. Its solubility is increased by addition 
of weak organic acids, citric or tartaric. 

Sodium Peroxide, Na 2 2 . — A white powder easily soluble 
in water, usually with evolution of more or less oxygen and forma- 
tion of hydrogen dioxide. 

Somnoform. — A general anesthetic administered in manner 
similar to chloroform; introduced by Dr. Rolland, of Bordeaux; 
consists of 60% ethyl chloride, 35% ethyl bromide, and 5% 
methyl bromide. (Dental Cosmos, Vol. XL VII, page 236.) 



186 MICROCEEMICAL ANALYSIS 

Stovaine. — Benzoylethyldimethyl-aminopropanol hydrochlo- 
ride, C14H21O2N.HCI, closely related to alypin, small shining 
scales freely soluble in alcohol or water. Incompatible with 
alkalies and all alkaloidal reagents. Can be sterilized by boil- 
ing. (Mod. Mat. Med., 2nd edition.) 

It melts at 17 5 C, is very soluble in water, and gives reaction 
similar to cocaine, which is also a benzoyl derivative. (U. S, D., 
page 1 66 1.) 

It is less powerful than cocaine and physiologically incom- 
patible with adrenalin. (Dental Cosmos, 1905, page 146.) 

Test. — Stovaine gives rather irregular but characteristic 
crystals with platinic chloride. (Plate IV, Fig. 4.) 

Suprarenal Glands. — The official preparation consists of 
dried glands obtained only from animals used for food by man, 
and which must contain not less than 0.4% nor more than 0.6% 
of epinephrine. 

Tannic Acid, or tannin, sometimes called gallotannic acid, 
is an astringent organic acid obtained from nutgalls. It may 
be obtained as crystals carrying two molecules of water, 
HC14H9O9.2 H 2 0. Tannic acid is a white or slightly yellowish 
powder soluble in about one part of water or 0.6 part alcohol. 
It is used as an alkaloidal precipitate, also in astringent washes. 
It may be detected by the addition of ferric solutions which 
form with it a black tannate of iron of the nature of ink. 

Thymol, C 6 H 3 (CH3)(OH)(C 3 H 7 ) 1:3:4. This is a phenol 
which occurs in volatile oils of thymus vulgaris (Linne). Melts 
at 44 C; sparingly soluble in water, easily in alcohol and 
ether. 

Tests. — It may usually be detected by its odor or by dis- 
solving a small crystal in 1 c.c. of glacial acetic acid, when, if 
six drops of sulphuric acid and one drop of nitric acid be added, 
the liquid will assume a deep bluish-green color. (U. S. D.) 

Thymol iodide, diiododithymol, (CeH^.CHs.CsHyOI^, a valua- 
ble antiseptic containing forty three per cent, of iodine. It is 



LOCAL ANESTHETICS AND ANTISEPTICS 187 

brown powder insoluble in water, slightly soluble in alcohol, 
easily soluble in chloroform or ether. 

Thymophen, a mixture of equal parts of thymol and phenol. 

Thyroids. — The dried, powdered, thyroid glands of animals 
used for food by man, freed from connective tissue and fat, 
containing not less than 0.17% or more than 0.23% of iodine, 
constitutes the official preparation used as a remedy in myxedema 
and other cases of perverted metabolism. 

Trichloracetic Acid occurs as deliquescent crystals, readily 
soluble in water. Distils at 195 C. and is a powerful caustic. 
Dilute solutions are recommended for treatment of pyorrhea. 

Tropa-cocaine is an alkaloid originally isolated by Giesel 
from the leaves of the small-leaved coca-plant of Java and intro- 
duced by Arthur P. Chadbourne, Harvard Medical School. 
Used hypodermically in normal salt solution. It is probably 
superior to cocaine, but rather more expensive. It is obtained 
as an oil which, when quite dry, solidifies in radiating crystals, 
melting at 49 C. It is easily soluble in alcohol. 

A number of commercial mouth-washes and local anesthetics 
will be given to the class for identification, the object being to 
familiarize the student with the more easily made tests for the 
principal ingredients of these preparations. Complete analysis 
will rarely be attempted. The following table, taken from the 
Druggist's Circular of June, 1910, may be helpful. 



i88 



MICROCHEMICAL ANALYSIS 



DIFFERENTIATION OF COCAINE AND ITS SUBSTITUTES. 





Iodine potassium 
iodide. 


Bromine water. 


Sodium hydroxide. 


Potassium per- 
manganate. 


Eucaine — a. 


Yellow-maroon 


Yellow precipitate, 


White precipitate, 


Violet precipitate, 




precipitate, 


soluble on heat- 


insoluble in ex- 


blackening 




soluble on 


ing. 


cess and on boil- 


quickly. 




boiling. 




ing. 




Eucaine — b. 


Deep-red pre- 


Yellow precipitate, 


White precipitate, 


No precipitate 
immediately; 




cipitate, solu- 


slightly soluble 


insoluble in ex- 




ble on boiling. 


on heating, re- 


cess and on 


color persists 






precipitated 


boiling. 


for a day. 






white on boiling. 






Cocaine 


Yellow-maroon 


Yellow precipitate, 


White precipitate, 


Violet precipitate. 




precipitate, 


soluble on heat- 


insoluble in ex- 


color persists 




soluble on 


ing. 


cess and on 


for one hour, 




boiling. 


• 


boiling. 


then deposits 
Mn0 2 . 
Violet precipitate, 


Novocaine 


Deep-red pre- 


Yellow precipitate, 


White precipitate, 




cipitate, solu- 


soluble on heat- 


insoluble in ex- 


blackening 




ble on boiling. 


ing. 


cess and on boil- 


quickly. 


Stovaine 


Deep-red pre- 


Yellow precipitate, 


ing. 
White precipitate, 


Violet precipitate, 




cipitate, solu- 


soluble on heat- 


insoluble in ex- 


blackening al- 




ble on boiling. 


ing. 


cess; aromatic 
odor on boiling. 


most immedi- 
ately. 


Nirvanin 


Deep-red pre- 


Yellow precipitate, 


Precipitate, very 


Precipitate, first 




cipitate, solu- 


soluble on heat- 


soluble in excess 


maroon, then 




ble on boiling. 


ing, but the 
liquid becomes 
red and gives an 
agreeable fruity 
odor. 


of the reagent. 


brown. 


Alypin 


Yellow-maroon 


Yellow precipitate, 


White precipitate. 


Bluish-violet pre- 




precipitate, in- 


soluble on gentle 


insoluble in ex- 


cipitate, slowly 




soluble on 


heating. 


cess and on boil- 


blackening. 




boiling; orange- 




ing. 






red deposit. 









CHAPTER XX. 
TEETH AND TARTAR. 

The chemical examination of teeth and tartar, while coming 
more properly under the head of physiological chemistry, will 
be considered in part in this place, as the tests made, especially 
on tartar, are practically all microchemical. The composition 
of the cement is practically that of true bone, the dentine and 
enamel differing principally in the proportion of organic matter 
which they contain. In all of these the presence of lime, phos- 
phoric acid, carbonic acid, and traces of magnesium and calcium 
fluoride may be demonstrated. The tartar contains a greater 
proportion of carbonic acid, less calcium phosphate, and much 
less organic matter than the teeth, taken as a whole, or than 
dentine, but about the same as enamel. According to Berzelius, 
sodium chloride and sodium carbonate may also be found. 

The composition of the different parts of the tooth sub- 
stance has been given as follows : 

flatten Ash ' Ca ^ ^- MgHPO*. CaC0 3 . 

Dentine 23.2 76.8 70 . 3 4.3 2.2 

Cement 32.9 67.1 60.7 1.2 2.9 

Enamel 3.1 96 . 9 90 . 5 traces 2 . 2 

Also traces of magnesium carbonate, calcium sulphate, fluorides, 
and chlorides. An increase in the percentage of calcium phos- 
phate of fluoride increases the hardness of the tooth, while an 
increase of calcium carbonate decreases the hardness. 

Potassium sulphocyanate, ferric phosphate, sulphites, and 
uric acid have been found in tartar, as additional chemical 
constituents, while after the solution of the mineral matter 

180 



190 MICROCHEMICAL ANALYSIS 

the presence of epithelium cells, mucus, and the leptothrix may 
be demonstrated by the microscope. 

According to Vergness, Du tartre dentaire, quoted by Gamgee, 
the tartar from incisor teeth and that from molars show decided 
difference in their content of iron and calcium phosphates, the 
analysis being as follows: 

Tartar of Incisors. Tartar of Molars. 

Calcium phosphate , 63 . 88-62 ,56 55.1 1-62 . 1 2 

Calcium carbonate 8 . 48- 8.12 7 . 36- 8 . 01 

Phosphate of iron 2.72-0.82 12.74- 4.01 

Silica 0.21- 0.21 0.37-0.38 

Alkaline salts o. 21- o. 14 0.37- 0.31 

Organic matter 24.99-27.98 24.40-24.01 



Deposition of Tartar Under Various Systemic 
Conditions. 

The presence of oxalates and urates have been reported 
in the black tartar from pyorrhea cases. The deficient oxidation 
and high acidity usually occurring in such cases is conducive to 
the production of large amounts of oxalic or uric acids in the sys- 
tem, not necessarily on the teeth, whether these substances have 
etiological relations to pyorrhea or not. 

The formation of ordinary hard tartar consisting princi- 
pally of phosphate and carbonate of calcium is accounted for by 
Dr. Percy G. Howe* as follows: An excess of calcium salts 
in the blood must be granted as one of the causes of calcification. 
These calcium salts are held in solution by two distinct factors : 
first, the excess of carbon dioxide; and second, by the presence 
of colloidal substances in suspension. This accounts for the 
fact that the loss of carbon dioxide does not universally precipi- 
tate the lime salts. Barille holds that calcium phosphate occurs 
in the blood as an unstable carbon phosphate which tends to 
decompose into calcium acid phosphate and bicarbonate, and that 

* Dental Cosmos, 1915, page 307. 



TEETH AND TARTAR 191 

in saliva we find both these salts held in solution by carbon 
dioxide as follows: 

Ca 3 (P0 4 ) 2 + 4H 2 C0 3 = H 2 + P 2 8 Ca 2 H 2 .2 C0 3 (C0 3 H) 2 Ca. 

Upon the escape of the carbon dioxide, the calcium precipitates 
as the tri-metallic phosphate if the solution is alkaline, and as 
dicalcic phosphates if the solution is acid; and, of course, the 
loss of carbon dioxide will at the same time result in the pre- 
cipitation of the neutral carbonate (CaC0 3 ). 

That the general systemic condition is also a factor in the 
deposition of tartar is indicated by the experience of Dr. Wright 
of the Harvard Dental School, who has watched for a succession 
of years the fairly uniform increase in tartar deposits from Oc- 
tober to June, and has found the vacation period marked by 
smaller amounts of deposit. 

Lactic and other organic acids have been found in minute 
quantities in tartar, but these as well as the qualitative tests for 
urates will be considered more in detail under the Chemistry 
of Saliva. 

Analysis of Teeth and Tartar. 

The substance for analysis should be reduced to a moder- 
ately fine powder by crushing in a mortar and a fair sample of 
the whole taken for each test. 

Moisture may be detected by the closed- tube test (page 105) 
and may be determined by accurately weighing out one gram 
of the substance in a counterpoised platinum dish or crucible 
and drying at ioo° C. to constant weight. 

Inorganic matter may be determined by careful ignition of 
dried substance; raise the temperature slowly till full red heat 
is reached; cool in a desiccator and weigh. 

Organic matter may be ascertained by difference. 

Lactates and other organic acids may be detected by careful 
crystallization and examination with the micropolariscope. 



192 MICROCHEMICAL ANALYSIS 

The several inorganic constituents may be demonstrated as 
follows: 

Phosphoric Acid. — Dissolve a little of the powdered sub- 
stance in dilute nitric acid; then to a few drops of the clear 
solution add an excess of ammonium molybdate in nitric acid. 
A yellow crystalline precipitate of ammonium phosphomolybdate 
will separate. Avoid heating above 6o° C, as the ammonium 
molybdate may decompose and precipitate a yellow oxide of 
molybdenum. 

Carbonic Acid may be detected by liberation of carbon 
dioxide and passing the gas into lime-water as described on page 
93 or with closed tube and drop of baryta-water, page 105. 

Chlorine may be detected in the dilute nitric acid solution by 
the usual silver nitrate test. 

Calcium and Magnesium may be separated and identified 
by the usual methods of analysis in the presence of phosphates. 

Test for calcium and magnesium as follows: Add to the 
hydrochloric acid solution an excess of ammonia; calcium phos- 
phate and magnesium phosphate are precipitated, white. Filter 
and to the filtrate add ammonium oxalate; a white precipitate 
shows lime, not as phosphate. Wash the precipitate produced 
by ammonium hydroxide, dissolve in dilute hydrochloric acid, 
and add ferric chloride carefully till a drop of the solution gives, 
when mixed with a drop of ammonium hydroxide, a yellowish 
precipitate. Nearly neutralize with sodium carbonate and add 
barium carbonate, which precipitates ferric phosphate. Filter, 
heat the filtrate, precipitate the barium with dilute sulphuric 
acid, and filter again. From the filtrate calcium is precipitated 
as white calcium oxalate by making it alkaline with ammonium 
hydroxide and adding ammonium oxalate as long as a precipitate 
is formed. Filter and add to the filtrate sodium phosphate, which 
precipitates magnesium as ammonio-magnesium phosphate, white. 

Laboratory Exercises may consist of the examination 
by microchemical methods of one or more samples of tartar. 



PART V. 

ORGANIC CHEMISTRY. 

CHAPTER XXI. 

THE HYDROCARBONS AND SUBSTITUTION PRODUCTS. 

Our work up to this point has been confined to inorganic 
chemistry excepting a few microchemical tests for organic 
substances. 

We are now to consider briefly the organic compounds which 
will serve as a basis for the intelligent study of physiological 
chemistry, and also some which are of peculiar interest in den- 
tistry. 

We shall touch but lightly on some of the subdivisions of the 
subject and take up a little organic chemistry proper, a little 
physiological chemistry, a little pathological chemistry, and 
from it all pick out such facts as may help us to a better under- 
standing of the problems of dentistry. 

As in many other departments of science, absolute rules for 
classification are impracticable; yet we may consider in a 
general way that the organic compounds are those containing 
carbon as a molecular constituent. The old conception that the 
organic compound must have been produced by a vital process 
of some sort (animal or vegetable) is of little value unless we con- 
fine our thought to substances found in nature only. 

The compounds of carbon are practically innumerable and 
very widely distributed, constituting the great bulk (aside from 
water) of all vegetable or animal substances. 

The carbon compounds contain the elements of carbon and 
hydrogen, and when these two only are present they are hydro- 
V 193 



194 ORGAXIC CHEMISTRY 

carbons. They more frequently contain carbon, hydrogen, and 
oxygen, and when the hydrogen and oxygen are present in the 
proportions in which they occur in water, the compound is a 
carbohydrate (with exceptions). 

In the chemistry of the animal body the majority of sub- 
stances which we meet contain carbon, hydrogen, oxygen, and 
nitrogen and often in addition sulphur or phosphorus. Many 
other elements, notably the halogens, and often the metals, may 
be found in organic compounds. 

The question of its composition is then the first one pre- 
senting itself in the consideration of an organic substance. 

The analysis of organic bodies may be made from two dis- 
tinct standpoints: first, to determine the various substances 
which may be separated from a given organized body, as from 
some part of a plant; secondly, to determine the constituent 
elements of one of the substances so separated. 

As an example of the first sort of analysis, we may find in a 
potato a certain basic principle (alkaloid), more or less water, 
and considerable starch. These may be called proximate prin- 
ciples, and the separation of them would be proximate analysis, 
while the second sort of analysis determines the composition of 
the starch molecule and is known as ultimate analysis. 

Qualitative Tests. 

Carbon. — The presence of this element may be shown by 
the " carbonization " obtained in the preliminary test, as given 
on page 104. 

Hydrogen shows itself by the production of moisture in 
these same tests. 

Nitrogen may or may not be indicated by the preliminary 
test. It may be detected with certainty by either of the fol- 
lowing methods : 

(a) Conversion into a cyanogen compound. 






THE HYDROCARBONS AND SUBSTITUTION PRODUCTS 195 

A small piece of thoroughly dried albumin together with 
a little metallic potassium is placed in a matrass, such as is 
described on page 34, and heated to redness for a few minutes. 
(Metallic sodium will work as well in most cases.) An alkali 
cyanide, which may be dissolved in water after breaking the 
tube, is formed, and by addition of a little yellow ammonium 
sulphide and evaporation to dryness on a water-bath will be 
changed to sulphocyanate, NH4CNS. If the dry residue is taken 
up with dilute hydrochloric acid, filtered, and tested with a 
drop of ferric chloride solution, the presence of the sulphocyanate 
is at once shown by the red color produced. 

(b) Conversion into free ammonia. 

Almost any nitrogenous substance may be made to evolve 
ammonia-gas by simply heating in a test-tube with several times 
its bulk of soda-lime. Test for ammonia by moistened red litmus 
paper or by odor. (This test is known as that of Wohler, also 
of Will and Varrentrap.) 

The Kjeldahl or moist combustion process is much employed 
as a quantitative method but may be used qualitatively as 
follows: The substance is heated in an ignition- tube with con- 
centrated sulphuric acid till a clear (not necessarily color- 
less) solution is obtained. The mixture is cooled, diluted with 
water, an excess of caustic soda added, and heat applied when 
ammonia is evolved, which may be detected by litmus paper or 
by odor. 

Sulphur and Phosphorus are first completely oxidized either 
by fusion of the substance with alkali nitrate and carbonate 
or by treatment in the wet way with fuming nitric acid or mix- 
ture of potassium chlorate and hydrochloric acid. The result- 
ing sulphate or phosphate is detected by the usual qualitative 
methods (page 95). 

A sulphur test may also be made by heating the substance 
with a little concentrated sodium hydroxide in the test-tube. 
A little sodium sulphide, which may be detected by dropping onto 



196 ORGANIC CHEMISTRY 

a bright silver coin or by testing with lead acetate solution, will 
thus be formed. 

Halogens. — Chlorine, bromine, and iodine cannot be de- 
tected in organic combinations by the ordinary qualitative test 
with silver nitrate and dilute nitric acid, but must first be con- 
verted into corresponding inorganic haloid salts. This may be 
done by heating the organic substance strongly with pure lime, 
when calcium chloride, bromide, etc., which may be dissolved in 
water and tested in the usual way, will be formed. (See pages 
96 and 97.) 

A test for chlorine or iodine may also be made by heating 
with copper oxide on a platinum wire in the Bunsen flame, chlo- 
rine giving first a blue then a green color to the flame. Iodine 
gives a green only (Beilstein). 

Test for presence of C, H, and S in dried albumin. 

Test for S by the caustic soda test. 

Test for P in casein precipitated from milk. 

Test a few drops of chloroform for the presence of chlorine. 

The Hydrocarbons. 

The hydrocarbons are organic compounds of carbon and 
hydrogen only. The simplest of these is marsh-gas or methane 
(CH4). The molecule of this substance consists of a single 
carbon atom with each of its four points of atomic attraction 
(valence) satisfied by an atom of hydrogen. 

H H 

X C X 
H / X H 

If one of these four atoms of hydrogen is replaced by a chlo- 
rine atom, for instance, we have a substitution product. Its for- 
mula will be CH3CI, its name monochlormethane or methyl 
chloride. If two molecules of methyl chloride are brought to- 
gether and the chlorine removed by metallic sodium the residual 






THE HYDROCARBONS AND SUBSTITUTION PRODUCTS 197 

molecules (methyl radicals) will unite, forming a new hydrocar- 
bon, as follows : 

2 CH3CI + Na 2 = 2 NaCl + C 2 H 6 (ethane). 

By a similar reaction we may form the third member of 
the series, C 3 H 8 (propane), from ethyl chloride (C 2 H 5 C1) and 
sodium; the fourth member, butane, C 4 Hi , from propyl chloride, 
etc. A tabulated list of the first five compounds of this series 
will plainly show their chemical relationship . 

CH 4 , methane or methyl hydride (CH 3 H). 
C 2 H 6 , ethane or ethyl hydride (C 2 H 5 H). 
C 3 H 8 , propane or propyl hydride (C3H7H). 
C4H10, butane or butyl hydride (C 4 H 9 H). 
C 5 Hi 2 , pentane or amyl hydride (C 5 HnH). 

Note that the various members of this series differ from one 
another by CH 2 ; that is, each higher compound contains one 
carbon atom and two hydrogen atoms more than its predecessor. 
This holds true through the series, and the compounds of this 
or any such series are termed homologues and the series ho- 
mologous series. Note further that any member of this series 
(which is known as the paraffin series) may be represented by 
the general formula C n H 2 „ +2 . This likewise holds true through- 
out the series, and a compound having sixty carbon atoms will 
have a formula of C 6 oHi 22 . The first four hydrocarbons of this 
series are gaseous at ordinary temperatures; from C 5 Hi 2 to 
about C16H34 the hydrocarbons are liquid; from C16H34 (melt- 
ing at about 18 ) up they are solids. 

Isomers. — When two or more compounds are of exactly 
the same molecular composition, or when two compounds have 
the same percentage composition the one being a multiple of the 
other, the compounds are said to be isomers or isomeric com- 
pounds. 

The isomerism of the first class is said to be metameric when 



iqS 



ORGANIC CHEMISTRY 



the atoms of the several compounds are not only the same in 
kind, but also the same in the number of each kind. For ex- 
ample, C12H22O11 is the formula for cane sugar; C12H22O11 is also 
the formula for milk sugar, and these two compounds have 
decidedly different properties, the difference being dependent 
upon the arrangement or relationship of the atoms in the mole- 
cule. Another example illustrating this difference may be 
found in the graphic formula for normal and isobutane given 
below. 



H 



H 



H 



H H H H 

1 1 1 1 




H 


C-C-C-C-H 




1 


1 1 1 1 


H 


-C -C 


H H H H 




1 1 
H H 



H 



/ 



C-H 

\ 



H 



Note that each molecule has an empirical formula of C 4 Hi ; 
the normal compound may be represented as CH 3 .(CH 2 )2.CH3, 
the iso-compound as CH 3 .CH.(CH 3 ) 2 . These will be found to 
have quite different physical and chemical properties. 

The isomerism of the second class is called polymeric and one 
substance is the polymer of another when the molecules are of 
the same percentage composition but of different molecular 
weights, for example, CH 2 is gaseous formaldehyde, (CH 2 0) 3 is 
its polymer or polymeric form, known as paraform, a white 
crystalline solid. 

The hydrocarbons of the paraffin series are known as straight 
chain or aliphatic hydrocarbons, their graphic formulae consist- 

I I I I 
ing of " chains " of carbon atoms, as butane, — C — C — C — C — , 

I I I I 
in distinction from the closed-chain or cyclic compounds as repre- 






THE HYDROCARBONS AND SUBSTITUTION PRODUCTS 199 



sen ted by the "benzene-ring" (page 
244) carbon nucleus with the carbon 
atoms united in a continuous closed 
chain or " cycle." 

The paraffins are called saturated 
hydrocarbons because they are inca- 
pable of forming addition products by 
absorption of chlorine, for instance, 
without first giving off an equivalent 
number of atoms of hydrogen. This 
is because of the complete " satura- 
tion " or union of every carbon 
" bond " with some other atom * 
Paraffin wax and mineral oil are mix- 
tures of saturated hydrocarbons and 
resist chemical action even of strong 
nitric acid or sulphuric acid. 

The name paraffin is derived from 
the two Latin words parvus, little, and 
affinitas, affinity. 

The natural sources of hydrocar- 
bons of the paraffin series are natural 
gas and crude petroleum, or rock oil. 
Many of these hydrocarbons exist as 
such in the petroleum, and some un- 
doubtedly are produced by the heat 
used to effect a separation of the va- 
rious compounds. This separation 
may be effected by distilling the oil 
in an apparatus similar to that pic- 
tured in Fig. 17, and is known as 

* Notice that while addition products of 
saturated hydrocarbon cannot be formed, sub- 
stitution products are easily possible. See 
page 203. 




Fig. 17. 



200 ORGANIC CHEMISTRY 

fractional distillation, the different hydrocarbons passing over at 
different temperatures. Separation by this method, however, is 
by no means complete, and the resulting products are them- 
selves mixtures of hydrocarbons, and are distinguished by physi- 
cal properties rather than by chemical composition. 

When crude petroleum is thus distilled, the following products 
are obtained: first, rhigoline, which comes over at a temperature 
of 20° to 22 C; then petroleum ether or benzine at from 50 
to 6o° C; then gasolene or naphtha at about 75 C; then one 
or two unimportant commercial products, and kerosene or burn- 
ing oil is obtained at 150 to 250 C. Above this, we may obtain 
paraffin oil or light lubricating oils; then the heavy lubricating 
or cylinder oils, and from the residue we obtain the solid sub- 
stances known as vaseline or petroleum jelly and paraffin of 
various degrees of hardness. 

The first five hydrocarbons of this series we will consider 
somewhat in detail, not only because they are important and 
comparatively common, but also because they serve as types of 
all other compounds of the series, and reactions which we study 
with these compounds are, as a rule, general typical reactions 
which may be produced with other members of the series. 

Methane, CH4, occurs as marsh gas in stagnant ponds or 
pools and is a constituent of " fire damp " in coal mines. It is 
a colorless gas, odorless when pure, and very slightly soluble 
in water. It may be prepared artificially by the decomposi- 
tion of anhydrous sodium acetate, with sodium hydroxide and 
lime. See reaction on page 382, Exp. 63. Methane burns in 
the air with the production of carbon dioxide and water 
CH4 + 2 2 = C0 2 + 2 H 2 0. 

Ethane, C 2 H 6 , the second member of the series, occurs natur- 
ally in a solution in crude petroleum, and can be artificially pre- 
pared by the electrolytic decomposition of a saturated solution 
of potassium acetate as follows : 

2 CH3COOK = C 2 H 6 + 2 CO2 + K 2 . 



THE HYDROCARBONS AND SUBSTITUTION PRODUCTS 201 

The free potassium, of course, decomposes water, liberating 
hydrogen gas which collects at the negative pole, and, if the 
solution contains sufficient potassium hydroxide, the carbon 
dioxide will be dissolved, allowing ethane to collect at the posi- 
tive pole. 

Ethane may also be made from a haloid derivative of marsh 
gas by the action of metallic sodium; that is, in CH4 we may 
replace one of the hydrogen atoms with iodine, forming CH 3 I, 
methyl iodide; then by treatment with metallic sodium, the 
following reaction will take place: 

2 CH3I -f 2 Na = C 2 H 6 + 2 Nal. 

Ethane is slightly more soluble in water than methane. It 
may be condensed to a liquid at a pressure of forty-six atmos- 
pheres. 

Propane, C 3 H 8 , also occurs in petroleum, and can be made by 
treating a mixture of ethyl iodide and methyl iodide with metallic 
sodium: 

C2H5I + CHgl + 2 Na = C 3 H 8 + 2 Nal. 

This is a general method for building up hydrocarbon com- 
pounds. Propane at ordinary atmospheric pressure is condensed 
to liquid at 17 below zero. 

Butane, C4H10, is the first of the series capable of existing in 
two forms, isomers. The structural formulae of these two com- 
pounds are shown in the illustration of the term isomer on page 
198. This compound and many of its higher homologues are 
of importance only in relation to some of their derivatives 
which will be subsequently studied. 

Unsaturated Hydrocarbons, 
double-bonded hydrocarbons. 

When a mixture of alcohol and strong sulphuric acid is 
heated, with the acid in considerable excess, water is with- 



202 ORGANIC CHEMISTRY 

drawn from the molecule of alcohol, and a gas found to have the 
formula C2H4 is produced. (See Exp. 64.) The name of this 
gas is ethylene; it occurs in coal gas and in traces in solution 
in crude petroleum. It is the first of a series of hydrocarbons 
which contain double-bonded carbon atoms. The double bond 
is assumed because it is found to be impossible to produce a 
lower compound of this series, such as CH 2 , which might be 
called methylene, but which would necessitate a bivalent carbon 
atom; also because the hydrocarbons of this series are capable 
of formation of addition products as well as of substitution 
products. 

Note that the formula of ethylene does not conform to the 
general formula of the paraffins (C n H 2 „+2), but is the first member 
of the new series of " unsaturated " hydrocarbons; the olefin or 
ethylene series with a general formula of C n H 2 „. 

The hydrocarbons of this series take their names from corre- 
sponding members of the paraffin series, with " ene " as a dis- 
tinguishing termination — ethylene, C2H4, propylene, C 3 H 6 , 
butylene, C 4 H 8 , etc. They are unimportant in dental or physio- 
logical chemistry. Some of the higher oxygenated compounds 
of this class are, however, of great importance, as olein, which 
is a constituent of vegetable and animal fats and oils, 

TRIPLE-BONDED HYDROCARBONS. 

A third series of the straight chain hydrocarbons is the 
acetylene series; these are triple bonded, and of course unsatu- 
rated, with a general formula of C n H 2n _2. 

The only members of this series of special interest are, first, 
acetylene, H — C = C — H, (C2H2), made from calcium carbide 
and water (see Exp. 67, page 382). It is poisonous, combining 
directly with the hemoglobin of the blood, has a disagreeable 
odor, and is inflammable; second, allylene, C3H4, derivatives of 
which occur in onions, garlic, mustard-oil, etc. 






THE HYDROCARBONS AND SUBSTITUTION PRODUCTS 203 

Haloid Derivatives of the Paraffins. 

Methane furnishes three chlorine substitution products which 
are more or less in common use : first, the monochlor-methane, or 
methyl chloride; second, the trichlor-methane CHC1 3 or chloro- 
form, and third, the tetrachloride of carbon CCI4. 

Methyl Chloride, CH 3 C1, may be made from methyl alcohol, 
zinc chloride, and hydrochloric acid. It is a colorless gas, con- 
densing to a liquid at 23 C; used as a spray in producing local 
anesthesia (page 182); also as a constituent of anesthetics, such 
as anesthol, somnoform, etc. 

Dichlor-methane, CH 2 C1 2 , also known as methylene chloride, 
has been used as a general anesthetic usually mixed in more or 
less chloroform and alcohol. Its use in this way is open to 
criticism because of its poisonous action, affecting the heart. 

Chloroform, CHC1 3 , trichlormethane, is a general anesthetic 
prepared by distilling a mixture of chlorinated lime and acetone. 
Alcohol and water were formerly used in place of acetone (see 
Exp. 70, page 383). While it is not regarded as inflammable, 
its heated vapor can be made to burn with a greenish flame. 
The reaction with alcohol is probably as follows: 4 C 2 H 5 OH 
+ 8 Ca(C10) 2 = 2 CHCI3 + 3 Ca (CH0 2 ) 2 + 5 CaCl 2 + 8 H 2 0. 

Methyl Chloroform, CH3CCI3, formed by replacing the hydro- 
gen atom of chloroform by a methyl group, CH 3 , has been used 
as an anesthetic. 

Tetrachloride of carbon is a colorless liquid used quite largely 
as a solvent. It also has anesthetic properties but like dichlor- 
methane, is dangerous because of its action on the heart. 

Methyl bromide, or monobrom-me thane, is used to some ex- 
tent as a constituent of anesthetics. 

Bromoform, CHBr 3 , tribrom-me thane, is prepared from 
bromine and a solution of alcoholic potash. Its properties are 
similar to those of chloroform, but it is more poisonous. 

Methyl Iodide, CH3I, is a heavy liquid, with pleasant odor, 
boiling-point 43 C; has been used somewhat as a vesicant. 



204 ORGANIC CHEMISTRY 

Iodoform, CHI3, tri-iodome thane, is a much-used and very 
valuable antiseptic. It is a light-yellow crystalline powder 
with characteristic persistent odor (Plate V, Fig. 1, page 204). 

Iodoform may be made by heating in a retort two parts of 
potassium carbonate, two of iodine, one of strong alcohol, and 
five of water, till the mixture is colorless, 

C2H5OH + 4 12 + 3 K 2 C0 3 = CHI3 + KCHO2 + 5 KI + 2 H 2 

+ 3 C0 2 . 

Iodoform is also produced from action of the above reagents 
with acetone in place of alcohol. This test is a very delicate 
one and advantage is taken of it in testing for acetone in saliva, 
which see. 

Cacodyl is an example of the arsenic derivatives of the 
hydrocarbons. It is one of several products which result from 
the distillation of a mixture of potassium acetate and white 
arsenic. Its composition is that of dimethylarsine, (CH 3 ) 2 As. 

Ethyl Chloride, C 2 H 5 C1, chlorethyl, may be made by dis- 
tillation of a mixture of alcohol and hydrochloric acid and 
purification of the distillate. It is extremely inflammable, boils 
at 12 C, and is used as a local anesthetic in similar manner to 
methyl chloride. Its higher boiling-point makes it the more 
convenient of the two preparations (see page 178). 

Ethyl Bromide, C 2 H 5 Br, prepared from alcohol, sulphuric 
acid, and potassium bromide. It is a heavy colorless liquid, 
does not burn, and has been used to considerable extent as a 
general anesthetic. 



PLATE V.— ORGANIC CHEMISTRY. 




Fig. i. 
Iodoform. 




Fig. 3. 
Urea Nitrate. 





Fig. 4. 
Hippuric Acid. 




Fig. 5. 
Benzoic Acid (sublimed). 



Fig. 6. 
Tyrosin. 



CHAPTER XXII. 
ALCOHOLS. 

If we substitute for one of the hydrogen atoms of methane, 
a hydroxyl group (OH), we shall produce the first of a series of 
alcohols, several of which will claim our attention. 

The alcohols may be considered as hydroxides of alkyl * radi- 
cals, CH3OH being methyl alcohol; C 2 H 5 OH being ethyl or 
ordinary alcohol; C3H7OH being propyl alcohol; and C5H11OH, 
amyl alcohol or fusel oil. 

The alcohols as a class may be prepared by the action of 
moist silver oxide on the corresponding halogen compounds; e.g., 

CH 3 Br + AgOH = CH 3 OH '+ AgBr. 

In many instances, the alkaline hydroxides will act in the 
same way. 

CH 3 Br + KOH = CH 3 OH + KBr. 

Alcohols treated with metallic sodium or potassium liberate 
hydrogen gas, forming compounds known as alcoholates; e.g., 

CH3OH + K = CH3OK + H; 
or C2H5OH +K = C 2 H 5 OK + H. 

While these compounds are, as just stated, called alcoholates, 
they may be distinguished, one from another, by using the name 
of the alkyl radical involved, and CH 3 OK will be potassium 
methylate, while C 2 H 5 OK will be potassium ethylate. 

Alcohols may contain more than one hydroxyl group, and, 
according to number of the OH groups, are termed mono-, di-, 

* Alkyl — a term used to denote any hydrocarbon radical as CH3-, C2H6-, C3H7-, 
etc. 

205 



206 ORGANIC CHEMISTRY 

tri-atomic, etc. Thus, ordinary alcohol, C 2 H 5 OH, is mono- 
atomic; glycol, C 2 H4(OH) 2 , is diatomic; glycerol, C 3 H 5 (OH) 3 , 
is triatomic, while mannite, C6Hs(OH) 6 , is a hexatomic alcohol. 

Alcohols may also be classified according to the relative 
position of the hydroxyl group. By this classification, we may 
have primary alcohols with OH replacing a hydrogen of the 
— CH 3 group; secondary alcohols with OH replacing the hydro- 
gen of a — CH 2 group; and tertiary alcohol with OH replacing 
the hydrogen of a — CH group. This may be illustrated by 
the formula of an alcohol of each class. CH 3 — CH 2 — CH 3 , 
being the hydrocarbon, a primary alcohol will have the formula 
CH 3 .CH 2 .CH 2 OH, and — CH 2 OH may be considered distinctive 
grouping of the primary alcohols. Again from the same hydro- 
carbon, if OH is substituted for an H of CH 2 then the secondary 
alcohol will be CH 3 -CHOH-CH 3 and -CHOH may be 
regarded as a distinctive group of this class. 

The tertiary alcohols, however, must be produced from com- 
pounds having at least four carbon atoms, as a CH group is 
only possible when there are sufficient carbon atoms to produce 
a forked chain; that is, in a compound with three carbon atoms, 
one must of necessity be placed between the other two, while 
with four carbon atoms, the carbons may be attached in a 
straight chain, such asC — C — C — C, or they may be arranged as 

.C 

a forked chain C — C , and by supplying the hydrogen atoms 

necessary to satisfy the valence of each carbon, in this latter 
chain we find a CH group. OH introduced in place of the 
hydrogen of this group gives us the tertiary alcohol, 

/CH 3 

ch 3 -coh; 

X CH 3 

Methyl Alcohol, CH 3 OH, (H-CH 2 OH),* wood spirit, car- 
binol, is a product of the destructive distillation of wood or can 

* Note that CH 2 OH is the " alcohol group" peculiar to this class of alcohols. 



ALCOHOLS 207 



be made synthetically from methane. It is a colorless, inflam- 
mable liquid, with a gravity of 0.802 at 15 C, with solvent 
properties similar to ordinary alcohol. It boils at 66°. 

Ethyl Alcohol, C 2 H 5 OH, (CH 3 -CH 2 OH), methyl carbinol, 
grain alcohol, or ordinary alcohol may be made by the action of 
silver hydrate on ethyl iodide or bromide as suggested on page 
205. It is made commercially by fermentation of various car- 
bohydrates and purified by distillation. Carbon dioxide is 
evolved as follows: 

C 6 Hi 2 6 = 2 C2H5OH + 2 C0 2 . 

95% alcohol has a specific gravity 0.8164, boils at about 
7 8° C, dissolves many inorganic salts, vegetable waxes, resins 
(not gums), oils, etc., and is miscible with water, ether, or chlo- 
roform. 

Propyl Alcohol, normal, CH 3 .CH 2 .CH 2 OH, occurs with amyl 
alcohol as a constituent of fusel oil, or may be prepared by 
general method with moist silver oxide. It is a colorless liquid, 
boils at 97 C. The iso-compound, CH3.CHOH.CH3, may be 
made by reducing acetone with nascent hydrogen; nascent 
hydrogen may be produced by sodium amalgam. 

Butyl Alcohol, C 4 H 9 OH, occurs in four isomeric forms. The 
normal alcohol is CH 3 .(CH 2 ) 2 .CH 2 OH. It is produced by the 
fermentation of glycerol. It boils at 117 C. The isobutyl al- 
cohol, (CH 3 ) 2 .CH.CH 2 OH, obtained from fusel oil, boils at 107 C. 

Amyl Alcohol, C 5 HnOH, (C 4 H 9 — CH 2 OH), consists of about 
87% of isobutyl carbinol and about 13% of an isomer known 
as active amyl alcohol. It is a colorless, oily liquid with a 
specific gravity of 0.818. It boils at about 130 C, and burns 
with a bluish flame. 

Fusel oil, or potato spirit, consists of amyl alcohol carrying 
traces of various other alcohols as impurities. 

Amyl alcohol is a valuable solvent and is largely used in the 
manufacture of artificial fruit flavors, banana essence, and the like. 



208 ORGANIC CHEMISTRY 

Oxidation of the Alcohols. 
Aldehydes. 

The first step in the oxidation of an alcohol consists not in 
the addition of oxygen but in the withdrawal of hydrogen; thus 
the oxidation of methyl alcohol produces formaldehyde (CH 2 0) 
and water. 

CH3OH + O = CH 2 + H 2 0. 

Aldehydes may be considered compounds containing an alkyl 

H H 

/ I 

radical and a distinctive group, — C ; thus CHO is formaldehyde, 

O 

CH 3 is acetaldehyde, etc. (Compare Alcohol, page 206.) 
I 
CHO 

Formaldehyde coagulates albumin and hardens gelatin; when 
used as a preservative it renders the proteins tougher and less 
digestible. 

Formaldehyde polymerizes, producing the paraform or para- 
formaldehyde of trade, trioxymethylene, with a probable for- 
mula of (CH 2 0) 3 . It also forms one lower polymer (CH 2 0) 2 and 
at least one higher, formose, a substance allied to glucose. 

Acetaldehyde, aldehyde, CH 3 — CHO or C 2 H40, the aldehyde 
from ethyl alcohol, may be made by addition of H 2 S0 4 to a 
mixture of alcohol and bichromate of potassium. It is a color- 
less, inflammable liquid with pungent etherial odor and boils 
at 22 C. 

Paraldehyde, (C 2 H40) 3 > a polymer of acetaldehyde, is a "color- 
less liquid with a strong pungent odor, soluble in 8.5 parts of 
water at 15 C, miscible in all proportions with alcohol, ether, 
and fixed or volatile oils." (U. S. P.) It is a valuable hypnotic. 

Chloral, CCI3CHO, trichlor aldehyde, is an oily liquid formed 
by action of dry chlorine gas on pure alcohol ; soluble in ether and 



ALCOHOLS 209 

chloroform, boiling at from 94 C. to 98 C, and forming, with 
a molecule of water chloral hydrate, CC1 3 CH0.H 2 0, a crystalline 
solid, and this is the chloralum hydratum of the pharmacopoeia 
(seepage 176). 

Chloral hydrate is decomposed by sodium or potassium 
hydrate with liberation of chloroform (see Exp. 87, page 387): 
CCla-CHO + KOH = CHCI3 + KCOOH (potassium formate). 
Upon warming a drop or two of aniline oil in an excess of 
alcoholic potash, chloral hydrate forms, first, chloroform, then 
phenylisocyanide, C 6 H 5 NC, the persistent disagreeable odor of 
which furnishes a delicate test for chloroform or chloral (see 
Exp. 88, page 387). By using CHCI3 as the reagent in place of 
the aniline, the same reaction becomes a test for aniline or 
organic compounds, from which aniline may be produced by 
heating with alcoholic potash as acetanilide. Other aldehydes 
from hexatomic alcohols are dextrose (glucose) and galactose. 
They are represented by the formula CH 2 OH- (CHOH) 4 -CHO, 
and will be considered more fully in a subsequent lecture. 

Ketones. 

The oxidation of secondary alcohols (page 206) will not yield 
aldehydes, but a class of substances known as ketones : 

(CH 3 ) 2 -CH-CHOH-CH 3 + O = (CH 3 ) 2 -CH-C : 0-CH 3 + H 2 0, 

A secondary alcohol. Methyl isopropyl ketone. 

Methyl isopropyl carbinol. 

or CH 3 - CHOH - CH 3 + O = CH 3 - CO - CH 3 + H 2 0. 

Isopropyl alcohol. Dimethyl ketone. 

The converse of each of these reactions is possible, and, by 
reduction of a ketone with nascent hydrogen (sodium amalgam), 
the secondary alcohol will be formed: 

CH 3 -CO-CH 3 + H = CH3-CHOH-CH3. 

Acetone. Isopropyl alcohol. 



2IO ORGANIC CHEMISTRY 

Likewise primary alcohols may be produced by the reduc- 
tion of aldehydes : 

CH3-CHO + H 2 = CH 3 -CH 2 OH. 

Acetaldebyde. Ethyl alcohol. 

Note that the grouping peculiar to ketones is = CO or — CO — . 

Acetone, or dimethylketone, CH 3 — CO — CH 3 , a colorless 
liquid of peculiar odor, boils at 5 6° C. and is made commercially 
by the dry distillation of acetate of lime. 

It occurs in the blood and urine of patients suffering from 
advanced diabetes. According to von Noorden, the acetone 
found in the blood is formed by an intracellular process and in- 
dicates an acid auto-intoxication and an insufficient utilization 
of carbohydrates. In the experience of the author, acetone 
may sometimes be found in the saliva when it cannot be found 
in the urine (for test, see Acetone under Saliva and Urine). 

Another ketone of interest is levulose, fruit-sugar, CH 2 OH — 
CHOH.CHOH.CHOH.CO.CH 2 OH, which, with glucose, wiU be 
studied later. 

While the oxidation of a primary alcohol will produce an 
aldehyde and the oxidation of a secondary alcohol will produce 
a ketone, the tertiary alcohol, by action of an oxidizing agent, 
is split into two new carbon compounds, that is, the chain is 
broken and simpler compounds usually including an organic acid 
are formed. 



CHAPTER XXIII. 
ETHERS. 

Ethers may be regarded as oxides of the hydrocarbon radi- 

C2H5 

cals, as / 0, or as anhydrides of the monatomic alcohols, 

C2H5 
water having been removed from two molecules of the alcohol: 
2 C 2 H 5 OH - H 2 = (C 2 H 5 ) 2 0. 

Ethers may be simple, mixed, or compound. The simple 
ether is illustrated above by the formula for ordinary or ethyl 
ether, where two radicals of the same kind are united by an 
atom of oxygen. 

In a mixed ether, these radicals will be of different kinds; 
as, for example, CH 3 — — C 2 H 5 , methyl-ethyl ether. 

The compound ethers are compounds of alcohol radicals 
with acid radicals, that is, the salts of alcohol radicals. The 
acid may be either organic or inorganic; thus, we have nitric 
ether, ethyl nitrate, C 2 H 5 N0 3 , and we have acetic ether, ethyl 
acetate, C 2 H 5 C 2 H 3 2 . The compound ethers are often called 
esters and form a large and important class of organic com- 
pounds. 

A general method for the preparation of simple and mixed 
ethers is that of distillation of the corresponding alcohols with 
sulphuric acid, as illustrated by experiment No. 94, page 388. 
They may also be produced by the action of silver oxide on the 
corresponding alkyl iodides: 

2 C 2 H 6 I + Ag 2 = (C 2 H 5 ) 2 + 2 Agl, 

also, by treating the sodium alcoholate with an alkyl iodide, 

211 



212 ORGANIC CHEMISTRY 

C 2 H 5 ONa + C 2 H 5 I = (C 2 H 5 ) 2 + Nal 

CH 3X 
or CHaONa + C 2 H 5 I - O + Nal. 

C 2 H 5 / 

Methyl Ether. — Methyl oxide, (CH3) 2 0, also known as 
formic ether, is isomeric with ordinary alcohol, and may be made 
in a manner similar to that used in the production of ethyl ether 
(q.v.). At ordinary temperature it is a gas, but liquefies at 
— 2o° C. (Bernthsen). It has been used as a general anesthetic, 
and the anesthesia is said to be profound and quickly pro- 
duced (U. S. D. from A. J. P., Sept., 1870). 

Methyl-ethyl Ether. — This name, besides indicating a 
definite compound as referred to in the preceding paragraph, 
has been applied to a mixture of methyl ether and ethyl ether, 
used for purposes of general anesthesia. 

Methylene Ether. — A name applied to a mixture of methyl- 
ene dichloride and ethyl ether, used as an anesthetic, but it has 
been found unsafe (U. S. D.). 

Ethyl Ether. — Ethyl oxide, (C 2 H 5 ) 2 0. The ether used for 
general anesthesia should contain not less than g$i% or more 
than 97!% of ethyl oxide, the remainder consisting of alcohol 
with a little water (U. S. P.). It is a light colorless liquid 
with a specific gravity of 0.715 at 25 C, with a boiling-point of 
about 35 C. It may be made by the action of sulphuric acid on 
ethyl alcohol, and from this fact has been known as sulphuric 
ether, but this name is, of course, incorrectly used, sulphuric 
ether being properly an ethyl sulphate, (C 2 H 5 ) 2 S0 4 . 

In the preparation of ether, sulphuric acid may be mixed with 
rather more than its own bulk of alcohol, the mixture heated to 
a temperature of from 130 to 13 8° C. in a suitable retort or 
still, the distillate (ether) being collected in a cold receiver. 

The reaction takes place in two steps, as follows: One mole- 
cule of acid and one of alcohol react to form ethyl sulphuric 



ETHERS 213 

acid (ethyl acid sulphate) and H 2 0, H 2 S0 4 + G>H 5 OH = 
C2H5HSO4 + H 2 0. Then the ethyl sulphuric acid reacts with 
a second molecule of alcohol to form ether and sulphuric acid, 
C2H5HSO4 + C2H5OH = (C 2 H 5 )2C + H 2 S0 4 . Thus the sul- 
phuric acid, from two molecules of alcohol, has produced one 
molecule of ether and is in condition to repeat the process, hav- 
ing been changed only to the extent of adulteration with one 
molecule of water. In accordance with this theoretic forma- 
tion of ether by simple dehydration of alcohol by sulphuric acid, 
provision is made for a continuous process, by the introduction of 
a constant supply of fresh alcohol into the retort during the dis- 
tillation, and so regulated that the total bulk of liquid is neither 
increased nor diminished. The product is then purified, and 
freed from water and traces of acid by redistillation over a mix- 
ture of lime and calcium chloride. 

Ether, according to the U. S. P. requirements, is " a trans- 
parent, colorless, mobile liquid with characteristic odor and a 
burning and sweetish taste." 

It is soluble in about twelve times its volume of water and 
in all proportions in alcohol, chloroform, petroleum ether, ben- 
zene, and oils. It is readily inflammable, and this fact, together 
with its easy volatility, makes it necessary to use considerable 
care when handling it. 

The action of sulphuric acid upon alcohol needs careful 
regulation; because there may be produced three other products 
in addition to the ethyl oxide already considered. These are, 
first, ethyl sulphuric acid, C 2 H 5 HS0 4 ; second, ethyl sulphate 
(C 2 H 5 ) 2 S0 4 , these being respectively the acid and neutral ethyl 
esters of H 2 S0 4 ; third, the hydrocarbon ethylene, C2H4. This 
latter compound is the first of the ethylene series of hydro- 
carbons with the general formula C n H^ n and containing " double- 

H\ /H 

bonded " carbon atoms, C = C or CH 2 = CH.CHs. 



214 ORGANIC CHEMISTRY 

These are unsaturated hydrocarbons (see page 201). Ethylene 
is produced by the action of an excess of concentrated sulphuric 
acid, which abstracts water from each molecule of alcohol 
(C2H5OH — H 2 = C2H4), whereas in the preparation of ether 
the more dilute acid abstracts water from two C 2 H 5 OH. 

Compound Ethers or Esters. 

Ester is the term applied to etherial salts; that is, compounds 
in which an alkyl group has taken the place of replaceable hy- 
drogen of the acid. They are produced by the action of the acid 
upon the alcohol which is as nearly as possible free from water. 
Such action by the halogen acids would produce the alkyl 
haloids already considered; for example, CH 3 OH + HC1 = 
CH3CI + H 2 0. As the water produces alcohol and hydro- 
chloric acid by action on CH3CI it must be removed as the 
experiment proceeds. 

The ethyl hydrogen sulphate is produced as an intermediate 
step in the preparation of ether, q.v. 

Ethyl nitrite, C 2 H 5 N0 2 , is a colorless liquid, boiling at 17 C. 
and is used in medicine as Sweet Spirits of Niter, which is an 
alcoholic solution containing traces of the ethyl nitrate, various 
oxidation products, and not less than 3.5% nor more than 4.5% 
of the ethyl nitrite. It is insoluble in water, but by action of 
boiling water or dilute alkalies becomes ethyl alcohol, C 2 H 5 N0 2 -f- 
KOH = C 2 H 5 OH + KN0 2 . See Exp. 97. 

Ethyl Acetate, CH 3 — COO.C 2 H 5 , is formed by heating ethyl 
alcohol, sulphuric acid, and acetate of sodium. This reaction 
constitutes a qualitative test for acetic acid or acetates, the 
odor of the ester being sufficiently characteristic to furnish a 
delicate test (page 100). 

The acetic ether of the U. S. P. is "a liquid composed of 
about 98.5% of ethyl acetate and 1.5% alcohol." 

Ethyl Butyrate, CH 3 - CH 2 - CH 2 - COOC 2 H 5 . This ester 
dissolved in ten parts of alcohol forms pineapple essence. It 



ETHERS 215 

may be made in a manner similar to the preparation of ethyl 
acetate, i.e., by heating together alcohol, butyric acid, and 
concentrated sulphuric acid. The production of the ester is 
likewise used as a qualitative text for the presence of the acid, 
and employed in the examination of gastric contents as follows: 
" Heat 10 ex. of contents with 5 c.c. of strong sulphuric acid 
and 4 c.c. of 95% alcohol; odor of pineapple indicates butyric 
acid." (Hewes.) 

Amyl Acetate and Amyl Butyrate may be obtained by heat- 
ing the respective acids with amyl alcohol (C5H11OH) and strong 
sulphuric acid. These esters may also be used in detecting the 
presence of the acid, amyl alcohol being used in place of ordinary 
alcohol. Amyl acetate gives the odor of pears, amyl butyrate 
that of bananas. 

Amyl nitrite, C 5 HnN0 2 , is a compound used in medicine to a 
considerable extent, usually administered by inhalation. The 
U. S. P. preparation contains about 80% of amyl nitrite. It is 
very soluble and inflammable. 

Fats are esters of glyceryl, C3H5, also called tritenyl, 
propenyl, etc. This radical forms with hydroxyl (OH) the pro- 
penyl alcohol, C3H5(OH) 3 , which is ordinary glycerin or glycerol. 

Glyceryl butyrate or butyrin, CHs-CCH^-COOCsHg, con- 
stitutes (together with smaller quantities of the glyceryl esters 
of capric, caproic, and caprylic acids) about 7% of butterfat. 
These esters are readily saponified by treatment with alcoholic 
potash; then, by decomposition of the potassium salts with 
H2SO4, the acids, being volatile, may be separated by distillation. 
The amount of volatile fat acids thus obtained is a valuable test 
for the genuineness of the butter. 

For further consideration of fats see Chapter XXXI. 



CHAPTER XXIV. 
ORGANIC ACIDS. 

If the oxidation of an alcohol is carried beyond the formation 
of aldehyde or ketone, i.e., if the aldehyde or ketone be oxidized, 
an organic acid results. The first atom of oxygen involved in 
this process does not become a constituent part of the new 
molecule, but simply withdraws hydrogen from the old (the 
alcohol), as shown in the formation of aldehydes on page 208. 
The second atom of oxygen, however, attaches itself to the 
molecule and does become a part of the new substance (the acid) : 

CH3 CH3 CH3 CH3 

I +0=1 + H 2 I +0=1 
CH 2 0H CHO CHO COOH 

Alcohol. Aldehyde. Aldehyde. Acid. 

The group —COOH is known as carboxyl and is the char- 
acteristic group of the acids. The hydrogen of the carboxyl 
differs from the other atoms of hydrogen in the molecule in that 
it is united to oxygen rather than to carbon, and constitutes the 
basic or replaceable hydrogen of the acid; hence acetic acid is 
monobasic, and the only possible salt of potassium, for instance, 
isCHs-COOK. 

The basicity of the acid depends on the number of carboxyl 
groups it contains. 

Among the monobasic acids of the fatty or paraffin series 
which we will study are the following: 

Representative Fatty Acids, 

H.COOH = formic acid or hydrogen formate; 

CH3.COOH = acetic acid or hydrogen acetate; 

216 



ORGANIC ACIDS 217 

C2H5.COOH = propionic acid or hydrogen propionate; 

C3H7COOH = butyric acid or hydrogen butyrate; 

C4H9COOH = valeric acid or hydrogen valerate; 
C15H31COOH = palmitic acid or hydrogen palmitate; 
C17H35COOH = stearic acid or hydrogen stearate. 

The acids of these series are represented by the general 
formula C n H 2n 2 . They all are monobasic; i.e., they contain 
only one atom of replaceable hydrogen. 

Formic Acid, (H.COOH), originally distilled from the bodies 
of ants (formica, from which the name is derived), is a colorless, 
easily volatile liquid. It may be prepared in the laboratory 
by heating oxalic acid with glycerol, when the oxalic acid breaks 
up into formic acid and C0 2 . 

C 2 H 2 4 = C0 2 + CHOOH. 

Carbon monoxide, passed over hot potassium hydroxide, 
results in the formation of potassium formate, 

CO + KOH = HCOOK. 

Also by treatment of ammonium carbonate with nascent hydro- 
gen (sodium amalgam), 

C0 3 (NH4) 2 + 2 H = HCOCKNH4) + H 2 + NH 3 
and 

HCOO(NH4) + NaOH = HCOONa + NH 3 + H 2 0. 

Formic acid, according to the above reaction, is apparently 
carbonic acid less one atom of oxygen, and the fact that formic 
acid acts easily as a reducing agent, taking away oxygen from 
other bodies and becoming H 2 C0 3 , is further proof of this 
relationship. 

Acetic Acid, CH3COOH, is obtained commercially by the 
oxidation of ethyl alcohol. It is the acid of vinegar, which, 
according to Massachusetts law, should contain 4^% of acid. 
Glacial acetic acid is a commercial name of- the acid contain- 
ing 1% or less of water; it is a colorless solid at a temperature 



2l8 ORGANIC CHEMISTRY 

below 1 5 C. The U. S. P. acetic contains only 36% (by weight) 
of the pure acid. 

Either one, two, or all three of the hydrogen atoms of the 
CH3 group may be replaced by chlorine, forming respectively 
the mono-, di-, and tri-chloracetic acids, the trichloracetic acid 
being used to a considerable extent in dentistry (page 187). 

Acetic acid, by the abstraction of water, forms an anhydride, 
C 4 H60 3 : 

2 HC 2 H30 2 = (C 2 H 3 0) 2 + H 2 0. 

This substance is of considerable importance in organic reac- 
tions. It is a colorless liquid with a boiling-point of 13 8° C, 
and, with the halogens, forms compounds such as acetyl choride, 
C2H3OCI, the radical C 2 H 3 being known as the acetyl radical. 

Propionic acid, CH 3 .CH 2 .COOH, is a colorless liquid, boiling 
at 140 C. According to Witthaus, it is best prepared by 
heating ethyl cyanide with caustic potash until the odor of the 
ester has disappeared: 

QH5CN + KOH + H 2 = QH5COOK + NH 3 . 

Then, by treatment with H 2 S0 4 , the propionic acid is liberated, 
and may be separated by distillation. 

Butyric Acid, C 3 H7COOH, occurs as a product of fermenta- 
tion of butter, or other animal fat containing butyrin; also 
from the decomposition of lactic acid, two molecules of lactic 
acid furnishing one of butyric acid, two of carbon dioxide and 
two of hydrogen (H 2 ). It is an occasional constituent of the 
gastric contents, and may be detected by formation of the ethyl 
ester (page 215). The pure acid is a heavy, colorless liquid with 
characteristic odor, soluble in water in any proportion. See 
page 215 for the glyceryl ester of butyric acid (butyrin); also 
for stearic and palmitic acids. 

Valeric Acid, C4H9COOH, may be made by the oxidation of 
amyl alcohol (C5H11OH). It is an oily liquid boiling at 174 C. 
It occurs as a constituent of valerian, and in consequence has 



ORGANIC ACIDS 219 

been called valeric acid. Its salts are used in medicine as seda- 
tives. 

The valeriate of amyl has an odor resembling that of apples, 
and is used in alcoholic solutions as apple essence. 

Palmitic Acid, Q5H31COOH, a solid " fat acid, " occurs as a 
glyceryl ester in butter (to a very slight extent), in olive oil, 
palm oil, and bayberry wax. Combined with certain alcohols 
it occurs in white and yellow wax; also in spermaceti. 

Palmitin, CsH^C^H^^, occurs in all animal fat and in 
large quantities in human fat. 

Stearic Acid, Ci 7 H35COOH[CH 3 - (CH 2 )i 6 - COOH], as glyceryl 
stearate or stearin, occurs in vegetable and animal fats, particu- 
larly in tallow. Stearic acid is only slightly soluble in alcohol 
or in ether. Its melting-point is 69. 3 ° C. 

Acrylic Acid Series, 

Acrylic acid, CH 2 : CH.COOH, is a type of the double- 
bonded acids. It is a liquid with boiling-point at 140 C. Nas- 
cent hydrogen breaks the double bond, forming propionic acid, 
CH3.CH2.COOH. Hydriodic acid will also break the double 
bond by direct union of its constituents, forming CH 2 I — CH 2 
— COOH, (/3-iodo propionic acid). 

Acrylic aldehyde, or acrolein, is a colorless liquid boiling at 
5 2 C. Its vapor has an irritating, pungent odor, sufficiently 
characteristic to be used as a qualitative test for glycerol, from 
which it is obtained by heating with KHS0 4 . 

The only other acid of particular interest in this series is 
oleic acid, C17H33COOH. It is an important constituent of oils, 
both animal and vegetable. 

Its glyceryl ester, C 3 H 5 (Ci7H33C0 2 )3, forms a large part of 
lard oil, cotton-seed oil, or any oil obtained by cold expression. 



220 



ORGANIC CHEMISTRY 



COOH 
I 
COOH 

Oxalic acid. 



Dibasic Acids. 
COOH 



i 
CH 2 

I 
COOH 

Malonic acid. 



COOH 

I 
CH 2 

I 
CH 2 

I 
COOH 

Succinic acid. 

Dibasic acids contain two carboxyl groups. These are refer- 
able to, and in many cases may be formed from, the diatomic 

CH 2 OH 
alcohols. Thus glycol, I , upon oxidation yields glycollic 

CH 2 OH 
CH 2 OH COOH 

acid, I , and oxalic acid, I 

COOH COOH 



Carbonic acid, O 



/ 



OH 



C , is dibasic in that it contains two 

X 0H 

atoms of replaceable hydrogen, though not two carboxyl groups. 

It is claimed that a molecule of this sort cannot exist because 

a single carbon atom cannot hold more than one hydroxyl group 

in combination. This acid has never been isolated, all attempts 

to separate it in the pure form resulting in the formation of 

carbonic acid gas and water. Its compounds (carbonates) are 

very common and very important, both in organic and inorganic 

chemistry. Organic salts of carbonic acid may be made by 

treating silver carbonate with alkyl iodide. 

/ OAg / OC0H5 

CO + 2 C 2 H 5 I = CO +2 Agl. 

x OAg x OC 2 Hs 

Oxalic Acid, which may be considered as a type of the di- 
basic acids, occurs as small, colorless crystals (four- or six-sided 
prisms), containing two molecules of water of crystallization 



ORGANIC ACIDS 221 

(H2C2O4.2 H 2 0); it is but slightly efflorescent, and, if carefully 
crystallized, is suitable for the preparation of standard acid 
solution. Salts of oxalic acid occur in many plants; the acid 
potassium oxalate, " salt of sorrel," is found in common red 
sorrel (Rumex acetora) and in wood sorrel (Oxalis acetocella). 
Oxalic acid in various combinations, often with lime, is widely 
distributed in articles of vegetable diet, particularly tomatoes, 
rhubarb, spinach, and asparagus; grapes, apples, and cabbages 
also carry oxalates but in smaller amounts. 

The source of oxalates in the system is twofold, — the in- 
gested oxalates and those produced by oxidation, incident to 
metabolism, the exact nature of which has not been clearly 
demonstrated (see Calcium and Sodium Oxalates, under Urine 
and Saliva) . 

Oxalic acid was previously made commercially by the action 
of strong nitric acid on starch or sugar; it is now prepared by 
heating cellulose (in form of sawdust) with a mixture of po- 
tassium hydroxide and sodium hydroxide, precipitating the acid 
as CaC20 4 , and decomposing the salt by sulphuric acid. The 
acid is then purified by repeated crystallization. 

Malonic Acid, COOH — CH 2 — COOH, is an oxidation product 
of malic acid (from apples), and is comparatively unimportant. 

Succinic Acid, COOH (CH 2 )2 — COOH, occurs in amber, from 
which it takes its name (Amber-Succinum) . It has been de- 
tected in the urine after asparagus and some fruits have been 
eaten. It occurs as colorless crystals, soluble in water, and only 
slightly soluble in ether. Succinic acid may be obtained by the 
saponification of ethylene cyanide, C 2 H4(CN) 2 , and is a dibasic 
acid containing four carbon atoms. It is a constituent of some 
transudates and cyst fluids. It occurs in the spleen and thyroid 
gland, and has been found in sweat and in the urine (Ham- 
mars ten). 

Pyro-tartaric Acid, formed by the distillation of ordinary tar- 
taric acid, is one of four isomers of formula C5H8O4, and is of 



222 ORGANIC CHEMISTRY 

interest only in its relation to some of the amino acids which 
result from protein digestion. Formula for pyro-tartaric acid 
is CH 3 - CHCOOH - CH 2 - COOH. 

Oxyacids. 

Hydroxy-acids, or alcohol acids, contain hydroxyl in place 
of one or more hydrogen atoms of the fatty acids. Thus we 
may consider 

Carbonic acid as hydroxyformic acid, HO — COOH; 

CH 2 OH 
Glycollic acid as hydroxyacetic acid, I ; 

COOH 

C2H4OH 
Lactic acid as hydroxypropionic acid, I ; 

COOH 

CHOH-COOH 
Malic acid (from apples) as hydroxy- I 

succinic acid, CH 2 — COOH 

CHOH-COOH 
Tartaric acid as dihydroxysuccinic acid, I 

CHOH-COOH 

Citric Acid, from lemons, limes, etc., is in a class by itself. 
It is a tribasic acid (has three carboxyl groups and one hydroxyl) ; 
the formula is C 3 H40H-(COOH) 3 . 

Glycollic Acid occurs in nature in unripe grapes, and possibly 
as antecedent to oxalates in the system (Dakin, Journal of Biol. 
Chem., 3.57). Glycollic acid is formed from glycol by oxidation, 
and from glycocoll, by action of nitrous acid. 

Nitric acid will oxidize glycollic acid to oxalic acid. 

Lactic Acid. — Oxypropionic acid, or i *-ethylidene lactic 
acid, CH 3 — CHOH-COOH, is ordinary lactic acid produced by 
fermentation of milk-sugar, etc. It occurs in the gastric juice 

* Optically inactive. 



ORGANIC ACIDS 223 

and in contents of the intestine, " particularly during a diet 
rich in carbohydrates," possibly in muscle and brain tissue 
(Foster). It is not volatilized at temperatures below 160 C. 

Sarcolactic or paralactic acid, d*-ethylidene lactic acid, 
occurs in meat extract. The presence of this acid causes the 
acid reaction of dead muscle, possibly of contracted muscle. 
It occurs in the blood and at times in the urine, and it is probable 
that it is this modification that may be found as lactates and 
acid lactates in the saliva and urine, the crystalline forms of 
which have been identified by Dr. E. C. Kirk of Philadelphia, 
by the use of the micropolariscopic method of Dr. Joseph P. 
Michaels of Paris. 

The optical activity of the lactic acids depends upon the 
presence of an asymmetric carbon atom. This asymmetric 
carbon, as the name implies, is one holding four different groups 
or atoms as illustrated by the following compounds. 

CH 3X /OH (C2H3O3K /OH H x /CH 2 .COOH 

c c c 

H' x COOH H 7 x COOH HO' > COOH 

Lactic Acid. Tartaric Acid. Malic Acid. 

The truth of the above statement regarding the optical 
activity of these substances may be demonstrated quite readily 
by the reduction of the hydroxyl group in sarcolactic acid when 
the inactive propionic acid results. 

CH3 \ / OH CH3 \ / H 

c c 

H 7 x COOH H' x COOH 

Active. Inactive. 

The optical activity consists in the power of the substance 
to turn the ray of polarized light to the right or to the left. 

Both of these acids form characteristic crystalline salts of 
zinc and of calcium. In cold water the zinc sarcolactate is 

* Dextrorotary. 



224 ORGANIC CHEMISTRY 

more soluble than zinc lactate; on the other hand, the calcium 
sarcolactate is rather less soluble than calcium lactate. 

P-Oxybutyric Acid, CH 3 - CHOH - CH 2 - COOH. If there is 
introduced into butyric acid, CH3 - CH 2 - CH 2 - COOH, an OH 
group, an oxybutyric acid results. If this alcohol group (OH) 
occupies the secondary or /? position (i.e., attached to the carbon 
atom twice removed from the carboxyl), the acid is the /3-oxy- 
butyric as above. 

By oxidation of the compound, the alcohol group is broken 
up and hydrogen withdrawn to form water, leaving a keto acid, 
CH3 — CO — CH 2 — COOH, known as diacetic acid. This in turn 
may give off carbon dioxide and become dimethyl ketone, or 
acetone, CH 3 — CO — CH 3 . These three substances, /3-oxybutyric 
acid, diacetic acid, and acetone, are classed in von Noorden's 
" Autointoxication," and in the works of other recent writers, 
as " the acetone bodies," and by this convenient term we may 
refer to them collectively. They occur in diabetic urine and, 
according to von Noorden, in other cases of perverted oxidation 
(not insufficient oxidation). 

Tartaric Acid is a dihydroxysuccinic acid, COOH — (CHOH) 2 
— COOH, obtained from grape-juice. 

We see by an examination of the graphic formula of this 
acid that it contains two asymmetric carbon atoms. 

mow ^ placing the hydrogen or the hydroxyl 

I on similar or opposite sides of the chain we 

H — C — OH see now it might be possible to obtain a 

I new form of isomerism depending on the 

OH — C — H relative position of the atoms in space and 

' not at all upon their attachment to other 

atoms of the molecule. This is found to 

be the fact and this sort of isomerism resulting only in differing 

physical properties such as optical activity has been called 

physical isomerism or stereo-isomerism. 

A mixture of equal weights of these two kinds of tartaric 



ORGANIC ACIDS 2 2 5 

acid crystallized together give an example of what is known as 
di- forms or racemic compounds. 

The double tartrate of sodium and potassium (Rochelle salt), 
KNaC 4 H40 6 , is much used in medicine. 

Tartaric acid combines with potassium and antimony to 
form tartar emetic, (KSbOC 4 H40 6 ) 2 , H 2 0. 

The " scale salts of iron" " ferri et ammonii tartras " and 
" ferri et potassii tartras," are prepared by dissolving freshly 
precipitated ferric hydroxide, in the acid tartrate of ammonia or 
potash, and, after evaporation to thick syrup, solidifying in 
thin layers on glass plates. 

Potassium Bitartrate, or acid tartrate, KHC4H4O6, is cream 
of tartar, and one of the few salts of potassium only sparingly 
soluble in water. Its commercial source is the wine-vat. 



Monobasic Amino Acids. 

Amino acids, formerly called amido acids, are characterized 
by an NH 2 group in place of hydrogen; for example, acetic acid is 
CH 3 CH 2 NH 2 

I . Amino acetic acid is I . These acids are of 

COOH COOH 

particular interest because of their close relationship to protein, 
many of them being among the cleavage products of protein 
hydrolysis. 

That many of the amino acids are formed as intermediate 
steps in the reduction of the complex protein molecules to urea 
is certain. 

A faulty metabolism, which stops short of normal oxidations, 
results in throwing these amino acids off in the urine or feces 
and their presence indicates abnormal conditions of one sort 
or another. 

NH 2 
Amino formic or carbamic acid, I , is a hypothetical 

COOH 



226 ORGANIC CHEMISTRY 

acid which would consist simply of an amino group, NH 2 , united 
to a carboxyl group, COOH. By the union of ammonia and 
carbon dioxide the ammonium salt of this acid is formed, 

NH 2 
2 NH 3 + C0 2 = I 

COONH4 

Ammonium carbamate is a constituent of commercial ammo- 
nium carbonate and an antecedent of ammonium carbonate in 
the hydrolysis of urea. 

Amino-acetic Acid, also called glycocoll and glycin, is ob- 
tained with other amino acids by boiling glue with either acids 
or alkalies.* It is also obtained, by the hydrolysis of glycocholic 
acid, from bile. 

Hippuric Acid (Plate V, Fig. 4) consists of benzoic acid 
united chemically to glycocoll, and may be produced syntheti- 
cally by the union of these two substances. 

Amino-Valeric Acid, CH 2 (NH 2 )-(CH)3-C200H, may be 
obtained with glycocoll from elastin, the protein of the elastic 
fibers, of tendons, etc.f Isomeric with amino-caproic acid is 
leucin, an amino-isobutyl-acetic acid. 

3 ^CH-CH 2 -CH(NH 2 )-COOH. 
CH 3 / 

Leucin, (CH 3 ) 2 CH.CH 2 .CHNH 2 .COOH, is an a-amino-iso- 
butyl-acetic acid and occurs, usually with tryosin, as a decom- 
position product of the proteins, including keratin and collagen. 
It results from the tryptic digestion of the hemipeptones and is 
regarded with other amino acids as among the antecedents of 
urea. Leucin only rarely occurs in the urine. When pure it 
crystallizes in thin, hexagonal plates, but as found in urine it is 
usually in the form of " spheres " represented by Fig. 2 of 
Plate V. 

* Bernthsen, Organic Chemistry. 

f Foster, Chemical Basis of the Animal Body. 



ORGANIC ACIDS 227 

Cystin, C6H12N2S2O4, is an amino acid occasionally found in 
the urine in diseases where the sulphur compounds fail to be 
properly oxidized. It occurs under these circumstances as reg- 
ular colorless hexagonal plates (Plate X, Fig. 6) . 

By the oxidation of cystin and subsequent splitting off of 
carbon dioxide taurine is produced. For occurrence of taurine 
see page 232. 

Tyrosin is a complex amino acid obtained from the decom- 
position of protein substances, particularly old cheese. It is oc- 
casionally found in urinary sediments as colorless needle-shaped 
crystals usually grouped as tufts or " sheaves" (Plate V, 
Fig. 6). 

Dibasic Amino Acids. 

Of this class of compounds two may be mentioned: amino- 
succinic, aspartic or asparaginic acid, COOH — CH 2 — CH(NH 2 ) — 
COOH, may be obtained from animal and vegetable proteins 
and in the pancreatic digestion of fibrin. 

Glutamic Acid is an amino-glutaric (pyrotartaric) acid, and 
occurs similarly to aspartic acid, except that it is not formed by 
pancreatic digestion. 



CHAPTER XXV. 
CYANOGEN COMPOUNDS. SULPHUR COMPOUNDS. 

Cyanogen, C 2 N 2 , is an intensely poisonous gas, colorless, 
heavy (specific gravity 1.81), and inflammable. It is very 
easily soluble in water or alcohol, forming unstable solutions, 
which, upon decomposition, give rise to various nitrogen com- 
pounds, among them ammonia, hydrocyanic acid, and urea. 

Cyanogen may be prepared by heating the cyanides of 
silver, mercury, or gold, or by the dry distillation of ammonium 
oxalate. 

Hydrocyanic Acid, HCN, may be produced by the fer- 
mentation of the glucoside amygdalin from bitter almonds; 
also from the kernel of peach-stones, cherry-laurel leaves, etc. 
Hydrocyanic acid may be formed by direct synthesis of C2H2 
(acetylene) and nitrogen. The synthesis is induced by passing 
electric sparks through the mixed gases. It is conveniently 
prepared in the laboratory by distilling a mixture of dilute sul- 
phuric acid with potassium ferrocyanide, K4Fe(CN) 6 + 5 H 2 S0 4 
= 6 HCN + FeS0 4 + 4 KHS0 4 . Hydrocyanic acid is a color- 
less, poisonous liquid, boiling at 26.5 C, with a characteristic 
odor often designated as a peach-stone odor. It is soluble in 
water and a two per cent, aqueous solution constitutes the acidum 
hydrocyanicum dilutum of the pharmacopoeia, also known as 
prussic acid. 

Potassium Cyanide (KCN or KCy) occurs in trade as a 

white solid, sometimes granular, more often as a powder. It is 

intensely poisonous owing to the dissociation of the salt and 

activity of the free cyanogen. 

228 



CYANOGEN COMPOUNDS. SULPHUR COMPOUNDS 229 

Potassium cyanide is decomposed by carbonic acid of the 
air with liberation of hydrocyanic acid. The aqueous solution 
of potassium cyanide hydrolyzes in two distinct ways : the most 
easily apparent at ordinary temperature is with the formation 
of hydrocyanic acid and potassium hydroxide giving the solu- 
tion an alkaline reaction: 

KCN + H 2 = HCN + KOH. 

Upon boiling a solution, the second hydrolysis may be 
demonstrated whereby ammonia and potassium formate are 
produced: 

KCN + 2 H 2 = HCOOK + NH 3 (Exp. 119). 

The organic cyanides are known as nitrils or isonitrils, accord- 
ing as the hydrocarbon radical is attached directly to the carbon 
or to the nitrogen of the cyanogen group. That is, methyl 
cyanide would be represented by CH 3 — CN, while the isocyanide 
would be CH 3 — NC (methyl carbamine); the nitrogen atom 
being in the first place trivalent, in the second quinquivalent. 

Of these two classes of compounds, the isocyanides are of 
much greater interest to the student of dental medicine owing 
to their relation to the isocyanates and to urea. 

Phenyl-isocyanide, C 6 H 5 NC, also known as isobenzonitril, 
is produced by warming aniline (C 6 H 5 NH 2 ) with alcoholic potash 
and chloroform, the intensely disagreeable odor of which is 
utilized as a test for chloroform or chloral hydrate (page 176); 
or, with chloroform and potassium hydrate, the production of 
this isocyanide may become a test for aniline, acetanilide (an- 
tifebrin) , and other derivatives of aniline. 

Potassium Ferrocyanide, yellow prussiate of potassium, 
K4Fe(CN) 6 , is obtained by heating animal refuse with a little 
over one- third its weight of potassium carbonate and scrap 
iron. The mixture is covered so as to exclude the air and after 
cooling the resulting mass is boiled with water and filtered. 



230 ORGANIC CHEMISTRY 

Upon evaporation of the filtrate potassium ferrocyanide will 
separate as yellow, four-sided crystals with a formula K4Fe(CN) 6 . 
3 H 2 0. The complex acid ion (Fe(CN)e) is not regarded as 
poisonous but can be made to dissociate by the addition of acid. 
See Exp. 122. By the action of strong sulphuric acid the radical 
is broken up and carbon monoxide is evolved. Dilute sulphuric 
acid will yield hydrocyanic acid according to the reaction on 
page 228. 

Potassium Ferricyanide, redprussiate of potassium, K 3 Fe(CN) 6 , 
contains iron in the ferric condition and may be made by oxidiz- 
ing the ferrocyanide by the action of chlorine gas. 

Cyanic Acid, HCNO, may be made by distillation of its 
polymer, cyanuric acid (HCNO) 3 . Cyanic acid cannot be made 
in the usual way by decomposition of its salts with mineral acids, 
since in the presence of water cyanic acid becomes ammonium 
carbonate. 

Potassium cyanate may be prepared by direct oxidation of 
potassium cyanide with lead oxide. 

Ammonium cyanate passes, upon heating, directly into 
urea. See Exp. 126. 

Isocyanic Acid, = C = N-H (carbimide) is supposed to be 
the acid of ordinary potassium and ammonium cyanates. 

Fulminic acid (C m N-O-H), isomeric with cyanic acid 
N = C — — H and isocyanic acid (O = C = N— H), is im- 
portant only because of its relation to the fulminates, which are 
explosive compounds of the acid, with some of the heavy metals, 
such as silver and mercury. 

Thiocyanic Acid or Sulphocyanic Acid. — In this acid and 
its salts, the atom of sulphur replaces the oxygen of cyanic acid 
in the empirical symbol (HCNS) ; but, graphically, the sulphur 
is attached to the basic element (metal or hydrogen) rather than 
to carbon: thus, K — S — C = N, that is, the sulphocyanate is 
not an isocompound. For occurrence and relations of HCNS in 
the human body, see chapter on Saliva. 



cyanogen compounds. sulphur compounds 231 

Sulphur Compounds. 

Mercaptan, an organic sulphhydrate. The name mercaptan 
comes from two Latin words signifying " taking mercury" 
(mercurium cap tans), because of compounds readily formed with 
mercuric oxide. Representatives of this class of compounds are 
found as derivatives of both the open and the closed-chain 
hydrocarbons. 

Ethyl mercaptan, thioalcohol, C 2 H 5 SH, is a type of this class. 
It is a colorless liquid, with bad odor, slightly soluble in water, 
boils at 37 C, and is used in the preparation of sulphonal. 

The mercaptans may be prepared by action of KHS on the 
alkyl haloids: 

C2H5I + KHS = C 2 H 5 SH + KI. 

The thioalcohols form potassium and sodium compounds 
similar to common alcohol, 

C2H5SH + K = C2H5SK + H. 

Mercaptol, a name which has been applied to the thioketones. 
The simple compounds of this class are not known as they form 
polymers very readily. A dimethyl-diethyl compound is pro- 
duced in the process for preparation of sulphonal. 

Thioethers are organic sulphides prepared in a manner 
analogous to that employed in the preparation of the thio- 
alcohols, the inorganic sulphide being used in place of the sulph- 
hydrate, for example: 2 C 2 H 5 Br + K 2 S = (C 2 H 5 ) 2 S + 2 KBr. 

Sulphones are oxidation products of organic sulphides: as, 

C TT O 

for example, ethyl sulphone S { . 

C 2 H B / ^o 
Sulphonal is a derivative of mercaptan as previously stated. 
It may be prepared by the action of acetone and ethyl mercaptan 
with hydrochloric acid and subsequent oxidation of the resulting 
product. 



232 ORGAXIC CHEMISTRY 

Sulphonic Acids as a class may be obtained by the oxidation 
of an organic sulphhydrate (mercaptan) . This oxidation may be 
produced by the action of nitric acid or potassium permanganate, 
and may be written as follows : 

C2H5SH + 3 = C2H5.SO2.HO. 

Taurine is an important sulphonic acid of the paraffin 

series. Its graphic formula shows it to be an amino ethyl sul- 

TTSO 
phonic acid, C 2 H4^ . Taurine is derived from taurocholic 

N NH 2 

acid by hydrolysis. This acid is representative of one of the two 

principal acid groups occurring in the bile, the salts of which may 

be found in pathologic conditions in the urine, or, according to 

Dr. J. P. Michaels and others, in the saliva. 



CHAPTER XXVI. 
AMINES OR SUBSTITUTED AMMONIAS. 

If one or more of the hydrogen atoms of ammonia, NH 3 , be 
replaced by a hydrocarbon group, the resulting compound is an 
amine; thus CH 3 — NH 2 is methylamine, and (CH 3 ) 2 NH is di- 
me thylamine. Trimethylamine, (CH 3 ) 3 N, has been found among 
the decomposition products of fresh brain, human liver, and 
spleen.* 

When one hydrogen atom only has been substituted in NH 3 
the amine is known as a primary amine or amino compound 
(containing the NH 2 group) . These may be prepared in a num- 
ber of ways, two of which we will consider. 

If alkyl iodides or bromides are heated with alcoholic am- 
monia, compounds are produced analogous in composition to 
the ordinary ammonium salts: 

CHJ + NH 3 = NH 2 CH 3 .HL 

Upon distilling the methyl ammonium iodide (of this reaction) 
with caustic alkali the amine results: 

NH 2 CH 3 HI + KOH = NH 2 CH 3 + Kl + H 2 0. 

The second method is by the action of nascent hydrogen 
upon alcoholic solution of the nitrils: 

CH 3 CN + 2 H 2 = C 2 H 5 NH 2 . 

The disagreeable odor of carbylamine constitutes a char- 
acteristic test for the primary amines. This is known as Hof- 
mann's Carbylamine Reaction and may be easily brought about 

* Vaughn and Novy, Cellular Toxins. 
2 33 



234 ORGANIC CHEMISTRY 

by warming the amine with a little chloroform and alcoholic 
potash. 

The secondary amines are those in which two hydrogen 
atoms of ammonia have been replaced as in dimethyl amine 
(CH 3 ) 2 NH. These compounds have also been called imines 
(imides) or imino (imido) compounds because they contain the 
"imino" group (NH). 

Imides are formed with a number of the dibasic organic 
acids. The one of greatest interest is perhaps the imide of 
succinic acid which may be produced by the following reaction. 
Ammonium succinate subjected to heat splits off 2 H 2 + NH 3 , 

CH 2 .CO x 
becoming I NH. The hydrogen of the imide group 

CH2.CCK 
may be replaced by metals such as potassium, silver, or mercury. 
Succinimide may also be produced by heating succinic acid, 
carbonic anhydride, and ammonia. This with mercuric oxide 
will give a white powder soluble in water, which is the mercuric 
succinimide largely used for the treatment of pyorrhea. 

The secondary amines may be produced by further action 
of alkyl iodides and the primary amines. By action of sodium 
nitrite and hydrochloric acid upon fairly strong solution of a 
secondary amine a nitrosamine is formed which, when mixed 
with phenol and strong sulphuric acid, gives a dark green solu- 
tion which becomes red upon dilution with water and this in turn 
becomes blue or green upon neutralization with a fixed alkali. 

Trimethyl amine formed with the methyl and dimethyl 
amines is a liquid with a not unpleasant odor. 

Diamines are derived from two molecules of ammonia, as 

/NH 2 

ethylene diamine, C 2 Ha 

X NH 2 

To this class of compounds belong many of the "ptomaines," 

produced by the putrefaction of organic matter, as putrescine 

(butylene diamine), CH 2 NH 2 — (CH 2 ) 2 — CH 2 NH 2 , and cadaver- 



AMINES OR SUBSTITUTED AMMONIAS 235 

ine (penta-methylene diamine), CH 2 NH 2 — (CH 2 ) 3 — CH 2 NH 2 . 
A large number of the ptomaines are aromatic compounds and as 
such will be referred to later. 

Amides. 

If the hydrogen of ammonia be replaced by an oxygenated or 
acid radical, an amide results; thus NH 2 (C 2 H 3 0) is acetamide, 
or this compound may be regarded as acetic acid, CH 3 — COOH, 
in which the OH has been replaced by NH 2 . 

It may be easier for the student to remember an amide as an 
organic acid with the OH of its carboxyl replaced by the "amido " 
or amino group NH 2 . 

Acetamide may be prepared by the action of strong am- 
monia upon ethyl acetate : 

CH 3 COOC 2 H 5 + NH 3 = CH 3 CONH 2 + C 2 H 5 OH. 

It forms colorless crystals soluble in both alcohol and water. 

Cyanamide (NH 2 in place of the hydroxyl of cyanic acid), 
NCNH 2 , is prepared by the action of ammonia on cyanogen 
chloride. The calcium compound is of commercial importance 
as a means of utilizing atmospheric nitrogen for agricultural 
purposes. CaC 2 heated with N 2 becomes NCNCa; this in a 
crude state is used as fertilizer. The calcium cyanamide by 
action of carbon dioxide, water, and soil bacteria becomes first 
urea, then ammonium carbonate. See page 237. 

Formamide, CHO.NH 2 , is a liquid miscible with both alcohol 
and water. It boils with partial decomposition at about 200 C. 
Upon heating quickly, it splits into carbon monoxide and am- 
monia. (Bernthsen.) 

Phenyl-formamide, CHO.NHC 6 H 5 , known as formanilide, 
occurs as yellow crystals soluble in water and in alcohol. 

Hydrazines. 
From diamide, NH 2 — NH 2 , or hydrazine, may be derived such 
substitution products as methyl-hydrazine, CH 3 — NH— NH 2 ; 



236 ORGANIC CHEMISTRY 

ethyl-hydrazine, C 2 H 5 — NH — NH 2 ; and phenyl-hydrazine, 
C 6 H 5 NH-NH 2 . 

This latter compound forms, with the monosaccharids and 
with many of the disaccharids, yellow crystalline compounds, 
known as osazones, which are precipitated in characteristic 
crystalline forms, recognizable upon microscopical examination 
and by their melting-points (see under Carbohydrates, page 261). 



CHAPTER XXVII. 



UREA AND URIC ACID. 



This substance forms about 50% of the total solids and 
about 85% of the nitrogenous matter contained in the urine. 
When we consider that only 5% of the nitrogenous waste passes 
off in the feces and 95% in the urine, the importance of urea as 
an index of the nitrogen excreted and of protein metabolism 
becomes apparent. 

Urea was the first organic substance synthesized from in- 
organic compounds. This was accomplished by producing a 
molecular rearrangement of ammonium isocyanate. The reaction 
is conveniently brought about by the double decomposition of 
potassium cyanate and ammonium sulphate and subsequent 
evaporation of the solution to dryness: 

2 CNOK + (NH4) 2 S0 4 = 2 OCN.NH4 + K 2 S0 4 . 



Then O 



C = N — NH4 (ammonium isocyanate) + heat = 

NH 2 

(urea). 



= C 



/ 



NH 2 



OH 



Urea is the amide of carbonic acid, = C f , and from 

x OH 

this type may be explained the rapid transformation of urea into 



ammonium carbonate in stale urine. O = C 



\ 



NH 2 
NH 2 



with one 



molecule of H 2 becomes 



C v or ammonium carba- 

X NH 2 

mate, and this, by addition of a second molecule of water, be- 

237 



238 ORGANIC CHEMISTRY 

/0NH4 
comes O = C or ammonium carbonate, (NH 4 ) 2 C0 3 . 

x ONH 4 

The last part of the reaction takes place whenever commercial 
" ammonium carbonate" [really a mixture of carbamate 
(NH4-NH2-CO2) and acid carbonate (NH4HCO3)] is dissolved 
in water. 

Urea crystallizes in long needle-shaped crystals of the rhom- 
bic system. It is insoluble in water, somewhat soluble in 
alcohol, and nearly insoluble in ether. It fuses at 13 2 , and at 
a somewhat higher temperature it gives off ammonia and am- 
monium carbonate, and at 160 leaves a residue of ammelide, 
cyanuric acid, and biuret. Urea is decomposed by solutions of 
the alkaline hypochlorites or hypobromites, being broken up into 
N, C0 2 , and H 2 0, as follows: 

CO(NH 2 ) 2 + 3 NaOBr = C0 2 + N 2 + 2 H 2 + 3 NaBr. 

Cyanuric Acid, N3C3O3H3, is a polymer of cyanic acid 

(NCOH), which is, at first, formed in the above decomposition. 

.CO - NH 2 
Biuret, H— N v , may be obtained by heating 

x CO-NH 2 

urea. When pure, it occurs as white, needle-shaped crystals. 

With NaOH and 1% CuS0 4 it gives the characteristic violet and 

rose-red shades obtained in the biuret reaction (Piotrowski's 

protein test). Exp. 189, page 406. 

Urea Nitrate may be precipitated from fairly concentrated 
urine by addition of HN0 3 . It separates in hexagonal crystals 
or plates, easily recognizable under the microscope (Plate V, 
Fig. 3, opposite page 204). 

Urea Oxalate. — Upon addition of a solution of oxalic acid 
to concentrated urine, crystals of oxalate of urea are precipi- 
tated. They are rather more easily obtained in characteristic 
forms (Plate II, Fig. 5, opposite page 170) than are the crystals 
of nitrate, and, in consequence, treatment with oxalic acid con- 
stitutes a better method for the qualitative detection of urea in 



UREA AND URIC ACID 239 

the body fluids than the nitric acid test formerly used. These 
crystals polarize light, and the use of the micropolariscope facili- 
tates their detection. 

Substituted Ureas. — The hydrogen of the amino group 
may be replaced by alcohol radicals forming what are known 

/NH 2 
as alkylated ureas: thus, O = C is methyl urea, 

X NHCH 3 

/NH 2 
O = C , ethyl urea, and one, two, three, or all four 

X NHC 2 H 5 

of the hydrogen atoms may be so replaced. 

When, in place of an alcohol radical, the acid radical is in- 
troduced, a class of compounds known as "ureides" results; thus 

/NH 2 

x NH(C 2 H 3 0) (acetyl urea). 

COOH 

In a case of a dibasic acid, such as oxalic, I , entering 

COOH 
into the reaction, one or both (OH) groups may be split off, form- 

ATTT 

ing in the first instance a ureide acid, as O = C ( , 

x NH.CO.COOH 
oxaluric acid, 

COOH /NH 2 /NH 2 

I +0 = C =0 = C + H 2 0, 

COOH X NH 2 x NH-CO 

I 

COOH 
/NH-C=0 
or, in the second case, a ureide, as O = C I parabanic 

x NH-C=0 
acid. 

If the residue of two molecules of urea enter into the composi- 
tion of the new molecule, the compound is a diureide. Of this 
class one of the most important is : 



240 ORGANIC CHEMISTRY 

Uric Acid, trioxypurin, C5H4N4O3. Its relation to urea may 

NH-CO 

I I 
be shown by the graphic formula O = C C— NH X 

I II C = O. 

NH-C-NH' 

Uric acid is also referable to a purely hypothetical base, "purin," 
by the use of which the relationship of xanthin, hypoxanthin, 
and other " purin" or nuclein bases is easily demonstrated. 

These bases are of great physiological interest, in that they 
form an unquestioned link between the decomposition products 
of the proteins, nuclein, etc., on the one hand, and uric acid 
and the urates on the other. 

Uric acid normally occurs in the urine combined with alkaline 
bases, also with traces of calcium and magnesium. It is insoluble 
in alcohol, ether, or dilute acids; practically insoluble in water, 
but much more soluble in solutions of urea or of glycerin. A 
solution of uric acid does not redden blue litmus. 

Purin is represented by the formula C 5 H 4 N 4 , or graphically 
N = C-H 

I I 

as H — C C — N — H . If we now break all double bonds ex- 

II II ^C-H 
N-C-N 

cept those linking two carbon atoms (4 and 5), we obtain a 
1 -N-C 6 
I I 
graphic nucleus, 2 = C C 5 — N — 7 , by numbering the atoms 
I II )C=8 

3 -N-C 4 -N-o 
of which we may easily designate any structural formula of the 
group; thus, 2 — 6 — 8, trioxypurin, is uric acid as above, while 

H-N-C = 
I I 
xanthin is 2 — 6, dioxypurin, = C C — N — H , and 1 — 3 — 7, 

I II )C-H 
H-N-C-INn 



UREA AND URIC ACID 241 

CH3-N-C = 

I I 

trimethyl-xanthin, = C C — N — CH 3 , is caffein and thein, 

I II ^C-H 

CH3-N-C-N 

alkaloids from coffee and tea. 

Traces of xanthin (2.6 dioxypurin), hypoxanthin (6 oxy- 
purin), guanin (2 imino, 6 oxypurin), adenin (6 amino purin), 
and heteroxanthin (7 methyl xanthin) have been found in urine, 
and, in cases of leukemia, many of them in increased amounts, 
notably xanthin, hypoxanthin, and adenin (Witthaus). 

Uric acid occurs in the urine; there are traces of it in the 
blood; and it is occasionally found, in the form of urates, in saliva. 
It is a dibasic crystalline acid, colorless when pure; but, in uri- 
nary sediment, it occurs generally as crystals, yellow to red, 
" whetstone "-shaped, and in various other forms (Plate X, Figs. 
1 and 2). The "brickdust" deposit occasionally found in urine 
consists of uric acid. It is insoluble in alcohol and nearly 
insoluble in water; but its solubility in water is increased by the 
presence of urea. 

Upon heating uric acid, urea and cyanuric acid may be ob- 
tained; NH 3 and C0 2 are given off. We are not to infer from 
this decomposition that the uric acid is an antecedent of urea 
in the animal body; for such is not the case, except possibly 
to a limited extent. 

Uric acid produces, upon oxidation, a variety of compounds, 
according to the temperature and the oxidizing agent employed. 

Chlorine, hot, yields cyanuric acid, C 3 N 3 (OH) 3 . Chlorine or 

/ /NHCO x \ 
bromine, cold, forms oxalic acid, alloxan (CC) , CO), 

\ ^NHCCK / 

parabanic acid j CO v I J and ammonium cyanate. 

\ NH-CO/ 

HNO3 in the cold, forms alloxan, alloxan tin, and urea (Witthaus). 



242 ORGANIC CHEMISTRY 

Uric acid may be detected by the murexide* test. See Exp. 
131, page 394. 

While uric acid is practically insoluble in H 2 and the acid 
urates only sparingly soluble, the uric acid in the system is 
apparently held in solution as an acid urate (NaHU) by the 
presence of the sodium phosphates, NaH 2 P0 4 and Na 2 HP0 4 , 
possibly also aided by the presence of some unknown organic 
combination. 

NaHU + NaH 2 P0 4 forms, at 38 C, a solution with an acid 
reaction; if, however, the mixture is cooled to room tempera- 
ture, the reaction becomes alkaline from Na 2 HP0 4 , and uric 
acid is precipitated (Bunge) : 

NaHU + NaH 2 P0 4 = Na 2 HP0 4 + H 2 U. 

Na 2 HP0 4 is a normal constituent of the blood, and a tendency 
to precipitate uric acid may be met by _the following reac- 
tion: Na 2 HP0 4 + H 2 U = NaH 2 P0 4 + NaHU. Because the acid 
urate of lithium is much more soluble in water than any of the 
other monometallic urates, lithium salts have long been used as 
uric acid solvents. But the fact that lithium solutions will 
precipitate from solutions of Na 2 HP0 4 crystals of Li 2 HP0 4 , has 
been made the basis for a claim that such use of lithium salts is 
without effect other than to decompose and render insoluble 
the alkaline phosphate, which has been acknowledged a valu- 
able factor in keeping uric acid in solution. While the disodic 
phosphate is regarded by many as superior to lithium salts as 
a uric acid solvent, the fact of comparative insolubility of 
Li 2 HP0 4 can hardly be regarded as conclusive evidence that 
lithium compounds are not effective. 

The following in regard to our need for "sarsaparilla" in 
the spring is given by Dr. E. C. Hill, of the University of Den- 
ver, in his text-book of chemistry, page 370: "Reduced alka- 

* Note. — Murexide is a definite chemical compound (CsHsNsOe) and may be 
produced from alloxantin, an oxidation product noted above. 



UREA AND URIC ACID 243 

Unity of the blood, as in winter from eating meats freely, throws 
uric acid out of solution to collect in the more acid tissues (spleen, 
liver, and joints). With the vernal tide of alkalinity (due to 
freer sweating, with excretion of fatty acids) these deposits are 
swept out in the blood-current, irritating the nerves and giving 
rise to 'that tired feeling.'" 



CHAPTER XXVIII. 
CLOSED-CHAIN HYDROCARBONS. 

In illustrating the simpler relationship of organic compounds 
we have, as far as possible, carefully avoided reference to the 
closed-chain or aromatic compounds, as the characteristic group- 
ings are more easily seen by the use of simple formulae. The 
distinguishing feature of the aromatic (also called cyclic) com- 
pounds is a nucleus consisting of a closed chain of atoms; this 
chain may contain three, four, five, six, or seven members, but 
the six-carbon ring is by far the most important, and the only 
one which we are to consider. 

The hydrocarbons of the aromatic series have, for a general 
formula, C n H 2n _ 6 , the simplest being benzene or benzol, C 6 H 6 ; 
and we may consider that the aromatic compounds are derived 
from this. The structure of the benzene molecule is repre- 
sented by Kekule's benzene ring. Note that ^ 
there are three double bonds, which of course | 
permit of addition products, as C 6 H 6 C1 2 , ben- ^C x 
zene di-chloride, etc. The substitution prod- H — C C — H 
ucts are, however, of far greater importance. I II 

Benzene, C 6 H 6 (benzol), is a colorless liquid H — C C — H 
from the "light-oil" obtained by distillation of C 

coal-tar. It boils at 8o°, has a gravity of 0.899, „ 

is soluble in ether, alcohol, and chloroform, but 
insoluble in water. It may be made pure by distilling an inti- 
mate mixture of benzoic acid and quicklime, and at a temper- 
ature of about 5 C. may be obtained as a crystalline solid, 
C 6 H 5 COOH + CaO = CaC0 3 + C 6 H 6 . (See Exp. 135, page 

395-) 

244 



CLOSED-CHAIN HYDROCARBONS 245 

Benzene may be considered as phenyl hydride, C 6 H 5 H, and 
similarly to the straight chain hydrocarbons two of these phenyl 
groups may be made to combine giving a hydrocarbon C12H10, 
known as diphenyl. Reaction 2 C 6 H 5 Br +2 Na = C12H10 + 
2 NaBr. 

Toluene, (toluol). — The next higher homologue of the series 
will be C 7 H 8 ; this is methyl benzene (C 6 H 5 CH 3 ) or toluene. 

The hydrocarbons of this series may be prepared in a manner 
similar to that used in the preparation of the hydrocarbons of 
the paraffin series. 

Toluene may be made by the action of metallic sodium upon 
a mixture of brombenzene and methyl iodide. 

C 6 H 5 Br + CH3I + Na 2 = C 6 H 5 CH 3 + NaBr + NaT 

Toluene is a colorless liquid boiling at iio°C, and yielding 
upon oxidation a benzene derivative; i.e., the CH 3 , or so-called 
side chain, is the part of the compound changed by oxidizing 
agents rather than the benzene ring, 

C 6 H 5 CH 3 + 30 = C 6 H 5 C0 2 H + H 2 0. 

Xylene, C 8 Hi (xylol) or dimethylbenzene, the next hydro- 
carbon of this series, exists in coal tar as a mixture of three 
isomeric compounds which may be graphically represented as 
follows: 

CH 3 CH 3 CH 3 

CH3 /\ 

CH 3 and 



These three possible positions of the second substitution are 
known as ortho-, meta-, and para-; thus, the first representation 
at the left will be ortho-xylene, or ortho-dime thylbenzene. The 
other two will be meta-xylene and para-xylene respectively. 

A trisubstituted benzene may be " adjacent," if the sub- 
stituted element or group is attached to the carbon atoms 



246 ORGANIC CHEMISTRY 

1 — 2 — 3, or " unsymmetrical " 1 — 2 — 4, or "symmetrical" 

i-3-5- 

A fourth isomer of dimethylbenzene would be an ethyl 
benzene, C6H5C2H5. This, upon oxidation, yields benzoic acid, 
in a manner similar to toluene. (Bernthsen.) 

Mesitylene, C9H12, is a trimethylbenzene. Only two isomers 
are possible. It can be prepared by dehydrating acetone by 
the use of sulphuric acid: 

3 C 3 H 6 - 3 H 2 = C 9 H 12 . 

Hydroxy Derivatives of the Aromatic Hydrocarbons. 

Phenol, carbolic acid, or oxybenzene, C6C5OH, obtained 
from the distillation of coal-tar, and used as an antiseptic and 
disinfectant. For properties and test, see page 183. Phenol 
acts like an acid, in that it forms salts with the metallic bases, 
C 6 H 5 OK, potassium phenolate, but it does not have an acid 
reaction on litmus paper or other indicators, i.e., it does not 
have free hydrogen ions when in solution, but belongs to the 
alcohols rather than the acids. 

The three di-hydroxybenzenes are all of interest and are 
graphically represented as follows: 

OH OH 







(~W tf'^-dihydroxy / \ weto-dihydroxy 

U-tl benzene or benzene or 

pyrocatechol | pw-rr resorcinol 



and 

OH 



£ara-dihydroxy 
benzene or 
hydroquinol 



OH 



The ortho compound is pyrocatechol. Its ethereal sulphate 
(acid sulphate) is given by Hoppe-Seyler as a constituent of nor- 
mal urine, and its monomethyl ether, guaiacol, C 6 H 4 OH — O — CH 3 , 



CLOSED-CHAIN HYDROCARBONS 



247 



is obtained from beech-wood creosote, of which it constitutes 
the greater part (60 to 90 per cent U. S. D.). Guaiacol and 
various compounds produced from it have been widely recom- 
mended for tubercular diseases. 

Pyrocatechol has been found to be the most practical reagent 
for the detection of oxidizing enzymes * in the saliva. 

Resorcinol is a white crysta line solid, becoming more or less 
colored upon exposure to the light. It melts at 118 C, and, 
in solution, gives a purple color with ferric chloride. Heated 
with sodium nitrate, it produces a substance known as " Lac- 
moid" which is used to a considerable extent as an indicator. 

The hydroquinol, or hydrochinon, is a white powder melt- 
ing at 169 C, and is largely used as a photographic developer. 

Pyrogallol, or trihydroxybenzene, C 6 H 3 (OH) 3 (1 — 2—3), mav 
be made by heating gallic acid, and because of this fact is usu- 
ally called pyrogallic acid. It is a white silky crystal which, 
like hydroquinol, is used as a photographic developer. Dis- 
solved in a solution of caustic potash it absorbs oxygen to a 
marked degree, and may be used as a reagent for the quantita- 
tive determination of oxygen in gas analysis. 

Phloroglucinol is another trihydroxybenzene, isomeric with 
pyrogallol but with the hydroxyl groups occupying positions 
1—3 — 5 in the ring. The formula is C 6 H 3 (OH) 3 (1—3 — 5). 

It crystallizes in rhombic prisms, soluble in water, alcohol 
and ether. This is used in physiological chemistry as a reagent 
with vanillin as a test for free hydrochloric acid. 

Thymol (3 methyl-6 isopropyl-phenol) , CeHsOH^CHa^CaHT^, 
is a solid of the nature of camphor, melting at 44 C, and is 
obtained from various volatile oils, particularly from the oil 
obtained from Thymus Vulgaris. It is very sparingly soluble in 
water. The addition of a little alcohol increases the solubility. 
It is largely used in the preparation of antiseptic dental prepa- 
rations, mouth washes, etc. 

* Journal of the Allied Dental Societies, Vol. 4, page 346, Dec, 1909. 



248 ORGANIC CHEMISTRY 

Cresol, C3H4CH3OH, is a hydroxy-toluene. Three isomeric 
compounds of this formula are obtained from the distillation of 
coal tar between 200 and 210 C. The ortho and para cresols 
are solid at ordinary temperatures, the ortho compound melting 
at 31 C, the para at 36 C. Meta cresol is a liquid which does 
not solidify unless under extreme conditions of cold and pressure. 

The cresols are similar to phenol not only in composition but 
also in physical and therapeutic properties; hence, cresol has been 
called cresylic acid, just as phenol has been called carbolic acid. 

A mixture of the cresols, said to be composed of meta cresol 
40%, ortho 35%, and para cresol 25%, constitutes the tricresol 
very largely used in dentistry as a germicide and antiseptic sim- 
ilar to carbolic acid. 

An emulsion of cresol, obtained by the solution of resin soap 
as an emulsifying agent, is known as creolin. Cresol is also a 
constituent of the disinfectant lysol. 

Tricresol is miscible with formalin in all proportions, and the 
mixture is recommended in the treatment of root canals. 



Nitrogen Derivatives. 

Benzidine, a diparadiamino derivative of diphenyl is made 
by the reduction of dinitrophenyl ; is a solid substance melting 
at 122 C, and is used as a reagent in testing for blood. 

Nitro-benzene, C 6 H 5 N0 2 , may be produced by treating ben- 
zene with a mixture of nitric and sulphuric acid at reduced 
temperature. (Exp. 137, page 395.) It is a yellow, oily liquid, 
with the odor of bitter almonds, commercially known as oil of 
mirbane, and used in the manufacture of aniline. 

Aniline or Amino-benzene, C 6 H 5 NH 2 . By reaction of nitro- 
benzene with nascent hydrogen, the N0 2 group becomes an NH 2 
group and aminobenzene or aniline is produced. Aniline, a color- 
less liquid, also called aniline oil, is important from a commercial 
rather than from a medical standpoint, as it forms the basis of 



CLOSED-CHAIN HYDROCARBONS 249 

the aniline dyes. When pure it is a colorless liquid, but changes 
quite rapidly when exposed to the light. It is used in testing for 
chloral and chloroform. It is slightly soluble in water, and 
easily soluble in alcohol and ether. At 8° C. it becomes a crys- 
talline solid. 

Diphenylamine, (CeH^NH, is formed by the substitution of 
the phenyl group for one of the amino hydrogens of aniline. It 
crystallizes from petroleum ether in white crystals which melt 
at 54° C. 

Acetanilide, C 6 H 5 .NH.COCH 3 , also known as antifebrine, 
may be produced by heating aniline and glacial acetic acid, 
crystallizes in colorless plates which melt at 115 C. 

Amino-phenol may be formed by the reduction of nitro- 
phenol by the action of nascent hydrogen (tin and hydrogen 
chloride). The para compound forms an ethyl ester which by 
action of glacial acetic acid gives phenacetine or para-acet- 
phenetidine, 

)C 2 H 5 . 

NH.CO.CH 



A 

CeH^ 



Picric Acid is trinitrophenol, C 6 H 2 .OH.(N0 2 )3. It may be 
formed by action of strong nitric acid, or mixture of sulphuric 
acid and nitric acid on phenol. It occurs as yellow plates slightly 
soluble in water, easily soluble in alcohol and ether, and is used 
in Esbach's reagent for the estimation of albumin in urine and 
as an alkaloidal precipitant. 

Salvarsan, (606) , arsenobenzol, more accurately paradiamino- 
dioxyarsenobenzene hydrochloride, is an arsenic derivative of 
benzene used in medical practice as a specific for syphilis. 

Aromatic Acids and Aldehydes. 

Benzoic Acid, C 6 H 5 COOH, was originally produced from gum 
benzoin, but may be made from hippuric acid (q.v.), which 
(from urine of horses) formerly constituted a commercial source. 



250 ORGANIC CHEMISTRY 

It is chiefly prepared, however, from toluene; it crystallizes 
in colorless plates or long prismatic crystals (from solution). 
It is sparingly soluble in cold water, more soluble in hot water, 
easily soluble in alcohol. It sublimes and is inflammable, burn- 
ing without residue. 

Benzoates of sodium, ammonium, lithium, and lime are all 
used in medicine. Benzoated or benzoina ted. lard is prepared by 
digesting gum benzoin in hot lard. This is much used as a base 
for ointments and keeps well. 

Benzaldehyde, C 6 H 5 — CHO, is a colorless liquid, soluble in 
alcohol and ether, and sparingly soluble in water. The U. S. P. 
oil of bitter almonds is practically benzaldehyde ; it is a volatile 
oil, very poisonous, and upon standing deposits benzoic acid 
from partial oxidation. 

Salicylic Acid, orthohydroxybenzoic acid, C 6 H4 — OH.COOH, 
is a white crystalline powder, odorless, irritating to mucous sur- 
faces, soluble in alcohol and ether, and in about 450 parts of 
water at 15 C. (U. S. D.). Salicylic acid may be made by 
action of carbon dioxide on sodium phenate and subsequent 
decomposition of the sodium salicylate. By heating rapidly the 
acid may be changed into phenol and carbon dioxide. 

Acetyl Salicylic Acid, CeH4.C2H3O2.COOH, known in medicine 
as aspirin, may be obtained by heating salicylic acid with acetyl 
chloride. It occurs as white needles slightly soluble in water, 
soluble in alcohol and ether. Aspirin is decomposed in the 
intestine, salicylic acid appearing in the urine twenty to thirty 
minutes after administration of aspirin. 

Salicylates have been used to considerable extent in various 
uric-acid diseases. Methyl salicylate constitutes 90% of natu- 
ral oil of wintergreen (Gaultheria). The alcoholic solution is 
essence of checkerberry. 

Salol is phenylsalicylate, C 6 H 4 OH.COO(C 6 H 5 ), a white crys- 
talline powder, practically insoluble in water and not decom- 
posed by the dilute acids of the stomach juices; but in the 



CLOSED-CHAIN HYDROCARBONS 25 1 

intestine it becomes salicylic acid and phenol, as follows: 
C 6 H 4 .OH.COOC 6 H 5 + H 2 - C 6 H 4 OH.COOH + C 6 H 5 OH. 

Gallic Acid, a trihydroxybenzoic acid, C6H 2 (OH) 3 COOH, 

(1 : 2 : 3 : 5), is prepared from tannic acid by action of dilute 
sulphuric acid, or by oxidation by exposure of powdered galls. 
It forms slightly brownish crystals; if pure, the crystals are 
colorless. At ordinary temperatures one part of acid is soluble 
in about one hundred parts of water, five parts of alcohol or 
twelve parts of glycerine. 

Tannic Acid, or Tannin, sometimes called di-gallic acid 
because its composition, Ci 4 Hi O 9 , corresponds to two molecules 
of gallic acid less one molecule of water, occurs in galls, in many 
astringent drugs and bark from various trees, as hemlock and 
oak. Tannic acid causes dark colored precipitate with ferric 
chloride, and precipitates gelatin, albumin and starch, differing 
in all of these particulars from gallic acid. (U. S. D.) 

Hippuric Acid, benzoyl glycocoll, C 6 H 5 CO.NH.CH 2 -COOH, 
occurs in traces in human urine, to a considerable extent in 
the urine of the herbivora, but not at all in that of the carnivora. 
It crystallizes in prismatic needles (Plate V, Fig. 4), often re- 
sembling crystals of ammonium magnesium phosphate; but as 
these latter only occur in neutral or alkaline urine and hippuric 
acid, usually in acid urine, there is little danger of confounding 
the two substances. Hippuric acid is hydrolyzed by the urease 
of fermenting urine, forming benzoic acid and glycocoll (amino- 
acetic acid) : 

C 6 H 5 CO - NH - CH 2 - COOH + H 2 

= C 6 H 5 COOH + CH 2 NH 2 COOH. 

Tryosin, C 6 H40H-CH 2 CH(NH 2 )-COOH, may be crystal- 
lized as fine silky needles. It is formed from protein substances, 
particularly casein and fibrin, both by the action of proteolytic 
enzymes and by putrefactive processes. It rarely occurs in uri- 
nary sediment; when found it is in bundles or sheaves (Plate V, 



252 ORGANIC CHEMISTRY 

Fig. 6, page 204), and is usually indicative of acute liver disease, 

phosphorus poisoning, etc. 

/COOH 
Phthalic Acid, C 6 Hi v , occurs in the form of rhombic 

x COOH 

crystals. By heating phthalic acid, phthalic anhydride may be 

obtained. 

/COv 

Phthalic anhydride, C 6 H 4 v ) O, heated with phenol and 

^CO^ 

sulphuric acid will give phenolphthalein, a valuable and familiar 

indicator in volumetric analysis. 

/HSO3 
Sulphanilic Acid, CeHi , is made by treating aniline 

X NH 2 

with concentrated sulphuric acid. It is a strong acid, occurring 
as white crystals, is soluble in water, and is used in the manu- 
facture of aniline dyes and also with naphthylamine as a reagent 
for the detection of nitrites. 

Phenyl Sulphuric Acid, C 6 H 5 HS0 4 , occurs only in combina- 
tion, the acid being unstable if attempt is made to isolate it. 
Its potassium salt is present in the urine as a product of in- 
testinal putrefaction. 

Phenyl-sulphonic Acid may be made by action of oxygen upon 
the sulph-hydrate, similar to the process described on page 232. 
C 6 H 5 SH + 30 = C 6 H 5 S0 2 HO. 

The potassium salt of this acid heated with potassium hydroxide 
is a commercial source of phenol. 

C 6 H 5 .S0 3 K + KOH = C 6 H 5 .OH + K 2 S0 3 . 

Phenol-sulphonic Acid. — When phenol is treated with 
several times its volume of cold, strong sulphuric acid, phenol 
OH OH 

sulphonic acid, | ] HS0 3 or I 1 results. If the mixture is 

HSO3 



CLOSED-CHAIN HYDROCARBONS 253 

heated for some time over a water-bath, the disulphonic acid 
results. This acid, warmed with a nitrate and the mixture 
treated with excess of ammonia, yields ammonium picrate, and 
constitutes a delicate test for nitrates present in drinking water. 
Phenol-sulphonic acid has been used in dentistry as a thera- 
peutic agent (as antiseptic and otherwise) . Such use is discussed 
in detail by Herman Prinz, M.D., D.D.S., in the Dental Cosmos 
for April, 191 2, with the conclusion that the ortho compound is 
several times more active than either the meta or para com- 
pounds; that a one per cent solution is about equal in antiseptic 
strength to a one per cent phenol solution, but in this strength it 
decalcifies the tooth structure, discolors the teeth, and should 
not be used in the mouth on account of its pronounced acid 
character. 

H 

HC C CH 

Indol, C 8 H 7 N, I 11 II , is produced from pro- 



HC C CH 

k C /x N 
H H 



tein by the putrefaction occurring in the small intestine, also by 
action of the proteolytic enzyme of the pancreatic juice (trypsin). 
The indol, by oxidation (after absorption from the intestines), 
becomes indoxyl, C 8 H 6 NO, which, with potassium sulphate, forms 
indoxyl-potassium sulphate, C 8 H 6 NKS0 4 , and, as such, is elimi- 
nated (in part) by the kidneys. This substance is a type of the 
so-called ethereal or conjugate sulphates, skatoxyl-potassium 
sulphate (skatol) and phenol-potassium sulphate being other 
compounds of this class. The ethereal sulphates are not precipi- 
tated by barium chloride in alkaline solutions, but may be de- 
composed by prolonged boiling with hydrochloric acid and then 
precipitated as usual. 



254 ORGANIC CHEMISTRY 

The oxidation of indoxyl produces indigo blue, and this fact 
is utilized in the qualitative test for indoxyl in urine (q. v.). 

Skatol, methylindol, C 6 H4\ /CH, occurs in similar 

manner to indoxyl, and likewise passes into the urine as an 
ethereal sulphate (skatoxyl-potassium sulphate). Skatol is a 
constituent of the feces and possesses a strong fecal odor. 

Heterocyclic Compounds. — The closed-chain or cyclic com- 
pounds are known as isocyclic or homocyclic when the atoms 
constituting the "ring" or nucleus of the molecule are all of 
the same sort (carbocyclic, if all of carbon), as has been the case 
in all the aromatic compounds which we have thus far taken 
up, i.e., the structure of compounds has been based upon the six- 
carbon or benzene ring. If the ring is made up of atoms of 
different sorts the compound is heterocyclic, and one or two of 
these are of importance. 

First, pyridin, C 5 H 5 N, which may be regarded as benzene, in 
which one CH group has been replaced by an atom of nitrogen: 

H 

// C x 
HC CH 

I II 
HC CH 

It is a liquid miscible with water, boiling-point 115 C. 
Second, quinalin, C9H7N, a colorless liquid. 

H H 

HC C CH 

I I II 
HC C CH 

H 



CLOSED-CHAIN HYCROCARBONS 255 

Upon one or the other of these two bases may be constructed 
the graphic formula of many of the vegetable alkaloids. 

A certain number of alkaloids, such as caffein and thein (tri- 
methylxanthin), are referable to the purin nucleus (page 240). 



PART VI. 

PHYSIOLOGICAL CHEMISTRY. 

CHAPTER XXIX. 

FERMENTS OR ENZYMES. 

Physiological chemistry treats of the substances which go 
to make up the animal body, the changes which these substances 
undergo in the process of digestion assimilation, and the final 
products of metabolism. 

This subject, like others, will receive our attention in out- 
line, with a view simply to enable the student to understand 
the conditions which at present seem to have the most direct 
bearing on dental science. The changes produced by the class 
of bodies known as ferments are of great importance and the 
first to be considered. 

If yeast is allowed to grow in a sugar solution of moderate 
strength, the sugar molecule is split into carbonic-acid gas and 
alcohol. The process is one of fermentation; the yeast is the 
ferment. There are various substances which cause similar 
splitting of complex molecules into simpler compounds.* 

The distinction between the organized and the unorganized 
ferments is no longer recognized, as it has been proved that the 
activity of an organized ferment is due to the presence of the 
unorganized ferment or enzyme, and we shall, by preference, 
refer to these substances as enzymes. 

The enzymes, as a class, possess certain general properties 
which should be remembered. 

* Occasionally fermentation may produce a synthesis (putting together) rather 
than an analysis (pulling apart). 

256 



FERMENTS OR ENZYMES 257 

First. Their action is limited to a very few substances; 
i.e., the enzyme from yeast, referred to above, will convert a 
few sugars only as indicated. They will not act in any other 
way nor upon other substances. 

Second. The enzymes act only at ordinary temperatures, 
usually showing the greatest activity at about the temperature 
of the animal body, 37 to 40 C. 

Third. Enzymes act only within very narrow limits as re- 
gards the chemical reaction (acid or alkaline) of the media. 

Fourth. Enzymes are destroyed (killed) by the heat of boil- 
ing water. 

Fifth. In regard to the nature of their composition, many of 
the enzymes are closely allied to the proteins. 

An enzyme may be classified according to the sort of work 
it does. Many of the chemical changes involved in the utiliza- 
tion of food consist of breaking up a complex molecule and by 
the use of a molecule of water forming new and simpler com- 
pounds. This sort of change is called " Hydrolysis" and an 
enzyme which will produce it is a hydrolytic enzyme. By 
hydrolysis or hydrolytic cleavage, the molecule of cane-sugar, 
C12H22O11, becomes two molecules of a simpler sugar, such as 
glucose, C 6 H 12 6 . daH^On + H 2 = 2 C 6 H 12 6 . 

Hydrolysis is not dependent upon enzyme action, as the 
same change is produced by prolonged boiling with very dilute 
mineral acids. 

Besides the classification of enzymes by the character of the 
work they do, the name of the substance acted upon may also 
be used to designate an enzyme; thus, a proteolytic enzyme 
produces a cleavage of protein substances. A lipolytic enzyme 
(lipase) splits the fat molecule, etc. 

Several of the digestive enzymes, notably the proteolytic or 
flesh-digesting enzymes, such as pepsin, trypsin, etc., exist in 
the animal cell, not as active agents, but as inactive parent 
enzymes which are called pro-enzymes or zymogens. Enzymes 



258 PHYSIOLOGICAL CHEMISTRY 

of this class are set to work (liberated from the parent sub- 
stance) by a class of substances known as "activators" (illus- 
trated by the enterokinase of the intestine, page 324). 

Neither the zymogen nor the activator has of itself any diges- 
tive action whatever; a provision which results in the preven- 
tion of autodigestion (autolysis) of the cells containing them. 

Another large and very important class of enzymes are those 
which produce oxidative changes. They may be divided into 
the oxidases, which produce direct oxidation, and the peroxidases, 
which produce oxidation only in the presence or by the aid of 
peroxide. 

Catalase is a term which has been applied to enzymes, similar 
in action to the peroxidases; i.e., they destroy a peroxide with 
the formation of molecular oxygen, although, according to 
Hammarsten, they differ from both the oxidases and peroxidases 
in giving no reaction whatever with guaiac. 

Oxidases have been found to exist in saliva, in milk, blood, 
nasal mucus, tears, and semen, in many of the organs, and also 
in the muscular tissue. They exist moreover in the vegetable 
kingdom from which the subject of oxidizing enzymes was first 
studied by Bertrand and Bourquelot* The urine, bile, and in- 
testinal secretions are said not to contain a ferment of this kind. 

The name of a specific enzyme usually ends in "-ase" as 
zymase, the enzyme contained in yeast; lipase, a fat-splitting 
enzyme; urease, the urine ferment. 

* "Enzymes and their Applications," Effrant: Prescott's translation. This 
work is also authority for statement immediately preceding regarding the source 
of oxidizing enzymes. 



CHAPTER XXX. 



Classification : 



Sugars 



CARBOHYDRATES. 

Arabinose 



Starch 



Gum 
Cellulose 



Xylose 

Dextrose 
Levulose 
Galactose 

Saccharose 
Maltose 

.Lactose 

(Starch 



( Glyco 



gen 



Dextrin 



Pentoses. 



Monosaccharides or monoses. 



Disaccharides or dioses. 



Polysaccharides or polyoses. 



Characteristics. — The monosaccharides are reducing bodies 
of either the aldehyde or the ketone type. The termination 
"ose" is applied to all sugars, and may also be used in designating 
the type; thus dextrose is an " aldose," while levulose is a 
"ketose;" i.e., dextrose is an aldehyde, containing the char- 
acteristic — CHO group, while levulose is a ketone containing 
the — C = group. 

The pentoses (C 5 Hi O 5 ) are represented by two important 
compounds, arabinose and xylose. The first of these occurs 
occasionally in the urine (pentosuria), and can be prepared by 
boiling gum arabic with dilute mineral acids. The second, 
xylose, has been obtained from the pancreas, but may be pre- 

259 



260 PHYSIOLOGICAL CHEMISTRY 

pared more easily from bran or straw by boiling with dilute 
hydrochloric acid (Exp. 162, page 400). 

The pentoses, as a class, boiled with dilute mineral acid 
(hydrochloric or sulphuric), yield furfuraldehyde by splitting off 
the elements of three molecules of water: 

C 5 H 10 O 5 - 3 H 2 = C5H4O2. 

The formation of furfuraldehyde can be easily demonstrated 
by various color reactions as given in experiment 162, page 400. 

The hexoses, CeH^Oe, also called monoses, occur quite gen- 
erally in nature (not true of the pentoses) . They constitute the 
various fruit sugars, and may be obtained by hydrolysis of the 
dioses and polyoses. 

They all reduce Fehling's copper solution (galactose less 
easily than the others), and they are all fermented by yeast 
(galactose more slowly than the others). 

. Dextrose or Glucose, C 6 Hi 2 6 , also known as grape-sugar 
and as diabetic sugar, occurs in grapes, honey, etc. It is formed 
by the action of diastatic ferments on the disaccharides ; also 
from many of the polysaccharides. Glucose thus occurs in the 
processes of digestion and constitutes the sugar of diabetic 
urine. It may be obtained commercially as a white solid, and 
also as a thick, heavy syrup, known as confectioners' glucose. 
The commercial glucose is prepared by the action of dilute acids 
on starch, when hydrolysis takes place, as follows: 

C6H10O5 + H2O = CeH^Oe. 

Dextrose can be oxidized first to gluconic acid (CH 2 OH.- 
(CHOH) 4 .COOH), and by further oxidation to diabasic sac- 
charic acid: 

COOH.(CHOH) 4 .COOH. 

This oxidation can be effected by the use of nitric acid. Sac- 
charic acid forms a definite soluble salt with calcium. Whether 



CARBOHYDRATES 261 

the fact has any bearing whatever on the relation of poor teeth 
and excessive use of candy has not been demonstrated. 

Tests. — Glucose boiled with Fehling's solution precipitates 
the red suboxide of copper (Cu 2 0) . 

Glucose responds to Molisch's test for carbohydrates, which 
is made with an alcoholic solution of a-naphthol and concen- 
trated sulphuric acid (Exp. 164). The monosaccharides, of 
which glucose is a convenient representative, may be distin- 
guished from the other carbohydrates by heating with Barfoed's 
solution (copper acetate in dilute acetic acid), which is reduced 
with precipitation of cuprous oxide. 

Heated with phenylhydrazine solution nearly to the boiling- 
point of water, glucose forms phenylglucosazone, which crystal- 
lizes, as the mixture cools, in characteristic yellow needles 
usually arranged in bundles or sheaves. (Plate VI, Fig. 1.) 

Osazones are the various compounds formed by the different 
sugars and phenylhydrazine when treated as above. They 
crystallize in fairly distinctive forms and furnish valuable tests 
for the sugars. The phenylhydrazine test is considered at least 
ten times more delicate than Fehling's test. Glucose readily 
undergoes alcoholic fermentation, yielding C2H5OH and C0 2 . 
(See Exp. 172, page 401.) 

Levulose, C 6 Hi 2 6 , or fruit-sugar, turns the ray of polarized 
light to the left, and to a greater degree than glucose turns it to 
the right. It occurs in honey and in many fruits, and is pro- 
duced with glucose by hydrolysis of cane-sugar. Levulose 
forms an osazone not to be distinguished from glucosazone. It 
reduces copper solutions in a manner similar to glucose, and, like 
it, is easily fermented by yeast. 

Galactose is the product of the hydrolysis of lactose, or milk- 
sugar, and some other carbohydrates. It is a crystalline sub- 
stance which reduces Fehling's solution and ferments slowly 
with yeast. 



262 PHYSIOLOGICAL CHEMISTRY 

DlSACCHARIDES OR DlOSES. 

Disaccharides have the general formula C12H22O11. They are 
converted into the monosaccharides by hydrolysis brought about 
either by action of enzymes or by boiling with mineral acid. 

Cane-sugar, C12H22O11, sucrose or saccharose, obtained from 
the sugar-cane (various varieties of sorghum), also from the 
sugar-beet (Beta vulgaris) and the sugar-maple (Acer saccha- 
rinum) . Cane-sugar is a white crystalline solid soluble in about 
1/2 part of water and in 175 parts of alcohol (U. S. P.)- It does 
not reduce copper solutions, nor does it form an osazone with 
phenylhydrazine ; but it is easily hydrolyzed with the formation 
of dextrose and levulose, and then, of course, the reactions 
peculiar to these substances may be obtained. It does not fer- 
ment directly, but, by the action of invertin contained in yeast, 
it takes up water, becoming glucose and levulose as above, these 
latter sugars being easily fermentable. 

Maltose, C12H22O11, or malt-sugar, is an intermediate prod- 
uct in the hydrolysis of starch, and by further hydration be- 
comes two molecules of dextrose : C12H22O11 + H 2 = 2 C 6 Hi 2 6 . 
It is formed in the fermentation of barley by diastase (the fer- 
ment of malt) , and with phenylhydrazine it produces an osazone 
distinguished from glucosazone and lactosazone by its micro- 
scopical appearance (Plate VI, Fig. 2) and its melting-point. 

Lactose, C12H22O11, obtained from milk, is a disaccharide 
with far less sweetening power than sucrose. It forms an 
osazone which crystallizes in small burr-shaped forms (Plate VI, 
Fig. 3). It reduces Fehling's solution, but does not reduce 
Barfoed's solution. It resists fermentation in a marked degree. 
Upon hydration it is converted into dextrose and galactose. 

Polyoses — Polysaccharides. 

Starch. — This well-known and widely distributed plant-con- 
stituent is a carbohydrate represented by CeHioOs, the actual 
molecule, however, being many times this simple formula. The 



PLATE VI. — PHYSIOLOGICAL CHEMISTRY 





Fig. i. 
Glucosazone. 



Fig. 2. 
Maltosazone. 




Fig. 3. 
Lactosazone. 





Fig. 4. 
Wheat Starch. 




Fig. 5. 
A, Corn starch; B, Rice starch. 



Fig. 6. 
A, Potato starch: B, Arrowroot starch. 



CARBOHYDRA TES 263 

microscopical appearance of the starch granule is quite charac- 
teristic, and recognition of the more common starches by this 
method is not at all difficult (see Plate VI, page 262). 

Starch is not soluble in cold water, but in hot water, or in 
solutions containing "amylolytic" enzymes, or in solutions 
containing certain chemical substances, as chloride of zinc or of 
magnesium, dilute hydrochloric or sulphuric acid, capable of 
forming hydrolytic products, the starch granules swell up, and 
ultimately dissolve, being converted into dextrose. The con- 
version, however, takes place in several well-defined steps, as 
follows : Soluble starch is first formed, answering the same chem- 
ical test with iodine (Exp. 245, page 416); next, erythrodextrin, 
which gives a red color with iodine solution; then achroo- and 
tnaltodextrin, which give no color with iodine, but react slightly 
with Fehling's copper solution; then maltose, also negative with 
iodine, but reacting strongly with Fehling's solution; and finally 
dextrose. 

Dextrin (C 6 Hi O 5 ) is a yellowish powder, also known as 
British gum; is formed from starch, as indicated above; con- 
stitutes to a considerable extent the " crust" of bread; is solu- 
ble in water, the solution giving a red color with iodine, and is 
also distinguished from starch by its failure to give a precipitate 
with solution of tannic acid. 

Glycogen, or animal starch, is a carbohydrate, with the gen- 
eral formula C 6 Hi O 5 , occurring principally in the liver, and to 
a lesser extent in nearly all parts of the animal body. Freshly 
opened oysters are a convenient source of the substance for 
laboratory demonstration. It occurs in horse-flesh in consider- 
ably larger proportions than in human flesh. 

Properties. — Glycogen is a white powder without odor or 

taste. It dissolves in water, producing an opalescent solution. 

It is closely allied to the starches of vegetable origin in that the 

products of its hydrolysis are dextrin * and ultimately dextrose. 

* Foster's Text-book of Physiology. 



264 PHYSIOLOGICAL CHEMISTRY 

It differs in its ready solubility in water, and in the fact that 
it is precipitated by 66% alcohol, also in its power of rotation, 
winch is much stronger than that of starch. 

Physiology. — Glycogen is formed by the liver, and stored by 
this same organ for future use. It is derived principally from 
carbohydrates, but may also be derived from proteins. It dis- 
appears during starvation. In dead liver or muscle it rapidly 
undergoes hydrolytic change with the production of a reducing 
sugar. 

Cellulose, C6H10O5, is a carbohydrate which occurs as a 
principal constituent of woody fiber, and which may be found 
in the laboratory in nearly a pure state, as absorbent cotton 
or Swedish filter-paper. It is insoluble in water, alcohol, or 
dilute acids; it may be dissolved, however, by an ammoniacal 
copper solution. It is converted into monosaccharides by acids, 
only after first treating with concentrated sulphuric acid, which 
partially dissolves it. Cellulose aids digestion in a purely me- 
chanical way by separating the digestible matter and allowing 
easier access of digestive ferments. The celluloses may be 
divided into three classes: those resisting hydrolysis and con- 
sequently lacking nutritive value, such as flax, cotton fibers, 
and hemp; those which hydrolyze slightly, which include the 
ligno-celluloses and may be utilized as food by herbiverous 
animals; the pseudo-celluloses, which are hydrolysed quite 
easily and may be digested by enzymes. 

When cellulose is treated with a mixture of nitric and sulphuric 
acids, it is converted into nitro-substitution products which are 
known as guncotton. The soluble cotton from which collodion 
is prepared, by solution in a mixture of ether and alcohol, is a 
mixture of tetra- and pentanitrates, while the more explosive 
but insoluble guncotton is a hexanitrate, formerly known as 
trinitrocellulose. 



CHAPTER XXXI. 
FATS AND OILS. 

Natural fats and oils of animal or vegetable origin are 
mixtures of several compound glyceryl ethers or esters (see page 
215), and by subjecting them to cold and pressure they may 
be separated into two portions, one solid with comparatively 
high melting-point, and the other liquid at ordinary tempera- 
tures. The solid portion is known as the stearopten, and the 
liquid as the eleopten, of the fat. Thus from beef-fat, we may 
express a fluid eleopten consisting largely of olein and obtain 
as a residue a stearopten, stearin. The stearopten of the vol- 
atile or essential oils are classed as camphors, on account of 
their resemblance to ordinary camphor. Menthol, from oil of 
peppermint, and thymol, from oil of thyme, are examples of this 
class of compounds, both of which are largely used in dental 
practice. 

Properties. — Fats are insoluble in water, easily dissolved by 
ether, chloroform, and carbon disulphide, less easily by alcohol, 
crystallizing on evaporation of the solvent. (Plate VII, Fig. 3, 
page 287.) They are emulsified by mechanical subdivision of 
the fat globules, in the presence of some agent which prevents 
their reuniting. The vegetable mucilages, soap, jelly, etc., are 
such emulsifying agents. On exposure to the air, fats and oils 
are more or less easily oxidized, which causes a separation of the 
fat acid. This produces an unpleasant odor or taste, and the 
fat is said to become rancid. 

Chemistry. — The principal organic acids entering into the 
composition of fat are Stearic acid, HC18H35O2, solid, white, 
without odor or taste, melts at 70 C; Palmitic acid, HCi 6 H 31 2 , 

265 



266 PHYSIOLOGICAL CHEMISTRY 

resembles stearic acid in its physical properties but melts at 
62 C; Oleic acid, HCi 8 H 3 2 , contains two CH= groups with 
double-bonded carbons in the middle of the chain. This last 
acid is fluid at ordinary temperatures and predominates in the 
softer animal fat. Its glyceryl ester, olein, constitutes seventy 
to eighty-five per cent, of human fat (percentage said to increase 
with age) and thirty-six per cent, of butter. 

Physiology. — Fats are not digested to any appreciable ex- 
tent until they reach the intestine; here they are broken up 
by a fat-splitting enzyme, emulsified, and to a slight extent 
saponified, after which they may be absorbed by the system 
(see Pancreatic Digest on) . 

Glyceryl Palmitate, CsH^CieB^iO^, tripalmitin; glyceryl 
stearate, CsH^CisEUC^, tristearin, and glyceryl oleate, 
C3H 5 (Ci8H330 2 )3, triolein; these in varying proportions make up 
the greater part of animal and vegetable fats and oils. 

The prefix "tri" is used because the "mono" and "di" 
compounds, as monopalmitin, C 3 H 5 (OH) 2 — C16H31O2, etc., are 
possible and may be prepared by synthesis. Triolein is liquid 
at ordinary temperature, solidifies at — 6° C, is a "double- 
bonded" compound, hence forms addition-products with the 
halogens as stearin and palmitin cannot do, since they are 
"saturated hydrocarbons." 

The amount of chlorine or bromine which a fat or oil can thus 
absorb is an index of the proportion of unsaturated fatty acids 
contained in it, and hence becomes a valuable method of identi- 
fication. Olive-oil and lard-oil contain large amounts of olein. 

Tripalmitin melts at 66° C, is usually obtained from palm- 
oil. Tristearin melts at 7 2° C, occurs with palmitin and olein 
in beef-fat, mutton- tallow, etc., the consistence of the fat being 
dependent upon the proportions of the constituent esters. 

The fats, stearin for example, may be split into glycerol and 
fatty acid by steam under pressure as follows : 

C 3 H 5 (C 18 H350 2 ) 3 + 3 H 2 = C 3 H 5 (OH) 3 + 3 HC 18 H 35 2 . 



FATS AND OILS 267 

A partial result of this sort is brought about by the fat-splitting 
enzyme (lipase) of the pancreatic juice (see Steapsin). 

Saponification of the fats by caustic alkali takes place as 
follows : 

C 3 H5(C 18 H 3 50 2 )3 + 3 KOH = C 3 H 5 (OH) 3 + 3 KC 18 H 35 2 . 

The potassium salts of the fatty acids constitute the soft 
soaps, while the sodium salts are in general the hard soaps. 
The " salting-out" process in soap manufacture brings about a 
double decomposition resulting in the production of ordinary soap. 

Volatile Oils do not contain the glyceryl base but rather a 
group of hydrocarbons known as the " terpenes." The formula 
is (C 5 H 8 )2, the most important of the group is Ci Hi 6 from oil of 
turpentine and many of the essential oils. 

The odor of the volatile oils seems to be dependent upon the 
presence of water and air; for example, oil of clove distilled over 
lime and in atmosphere free from oxygen has little odor. The 
presence of oxygen and moisture restores the characteristic odor. 

Lecithin has been classified as a phosphorized fat; it occurs 
in nervous tissue, in the bile, and is obtained in considerable 
quantity from the yolk of eggs. It contains two fat acid radicals 
combined with glycerol, phosphoric acid and choline. Lecithin 
is soluble in chloroform, alcohol, ether and benzene, and may be 
obtained in crystalline form from the alcoholic solution. The 
fatty acid radicals are not always the same or necessarily alike. 
Lecithin may be represented by the following formula: 

CH2 — Cl7H 3 5C02 

I 

CH — Ci7H 33 C(j2 
I 

CH 2 
I 
= P-OH.O 
I 

C2H4 
I 
(CH 3 ) 3 N-OH 



268 PHYSIOLOGICAL CHEMISTRY 

and its decomposition by the following reaction: 
CuHgoNPOg + 3 H 2 = 2 C 18 H 36 2 + C 3 H 9 P0 6 + C 5 H 15 N0 2 

Lecithin Stearic Glycero- Choline 

acid phosphoric 

acid 



CHAPTER XXXII. 



PROTEINS. 



Protein * is a general term used to designate the nitrogenized 
bodies which constitute the greater proportion of animal tissue. 

While meat and " protein" are usually associated, it must 
not be forgotten that meat is not the exclusive source of protein, 
for we usually find protein in vegetable substances and often to 
a considerable extent. 

Unlike the other two great divisions of food substances (carbo- 
hydrates and fats), the structure of the protein molecule is so 
complex that with a few exceptions of the simplest kind its 
representation has not been attempted. 

The protein molecule contains nitrogen (often as the amino 
group NH 2 ) in addition to the carbon, hydrogen, and oxygen of 
the carbohydrates and fats. It frequently contains sulphur, 
often phosphorus, and occasionally the metallic elements, par- 
ticularly iron. 

As examples of the complexity of protein molecules, the 
following proposed formulas are given in Hawk's Physiological 
Chemistry. 

Serum albumin, C450H720N116S6O140. 

Oxyhemoglobin, C 6 58Hii8iN207S 2 Fe02io. 

While a classification of proteins according to their chemical 
composition is at present practically impossible, the following 
may be of interest. 

After Hofmeister, Ergebnisse der Physiologie, Jahrg. I. 

* The term proteid was formerly used instead of protein, but in accordance 
with the recommendations of the Committees of the American Physiological and 
Biochemical Societies, it has been abandoned. The classification and definitions 
herewith given are taken from their recommendation as printed in Science, Vol. 
27, No. 692, page 554. 

269 



270 PHYSIOLOGICAL CHEMISTRY 

I. Groups of the Aliphatic Series. 

A. Group containing C, N, H. 

The only representative known is the guanidine radical 

(CNH).NH 2 . 

B. Groups containing C, N, H, O. 

1. Amino-acids. 

(a) Monamino-acids. 

1. Monobasic monamino-acids, C„H 2 „+iN0 2 . 

C 2 is glycocoll. 

C3 is alanin. 

C 5 is aminovalerianic acid. 

Ce is leucine, which occurs universally. 

2. Dibasic monamino-acids, C w H 2n -iN04. 

C 4 is asparaginic acid. 
C 5 is glutaminic acid. 

(b) Diamino-acids (all monobasic acids). 

C 2 is diaminoacetic acid (rare). 
Argynine (guanidine-a-aminovalerianic acid). Here the 
diamino-acid is combined with the guanidine radical, 

NH 2 .NH.C.NH.CH 2 .(CH 2 ) 2 .CH.NH 2 COOH. 

Lysine (a-e-diaminocapronic acid), 

NH 2 .CH 2 .(CH 2 ) 3 .CH.NH 2 .COOH. 

2. Amino-alcohols. 

Glucosamine, C 6 Hn0 5 (NH 2 ), a hexose into which 
NH 2 has entered the carbohydrate group of the 
protein molecule. 

C. Groups containing C, N, H, O, S. 

Cystein, amino thiolactic acid, CH 2 .SH.CH(NH 2 ).- 

COOH. 
Cystin, the sulphide of cystein, CeHi 2 S 2 N 2 04. 
a-thiolactic acid. 



PROTEINS 271 

II. Groups of the Aromatic Series. 

A. Phenylalanin, C 6 H 5 .CH 2 .CH(NH 2 ).COOH. 

B. Tyrosin, C 6 H 4 .OH.CH 2 .CH(NH 2 ).COOH. 

III. 

A. Pyrrol group. 

1. a-pyrrolidine carbonic acid, 

CH - CH - CH - CH.COOH 



NH 



B. Indol group. 

1. Indol, see page 253. 

2. Skatol (methyl indol), see page 254. 

3. Tryptophane (indolaminopropionicacid), 

C n H 12 N 2 2 . 

4. Skatosin, Ci Hi 6 N 2 O 2 . 

C. Pyridin group. 

Pyridin, see structural formula on page 254. 

D. Pyrimidin group. 

Histidin : structural formula probably 

NH CH 

I II 

CH = C-N-CH 2 -CHNH 2 -COOH. 

Excepting the carbohydrate group, and perhaps the pyridin 
and pyrimidin groups, which are absent in a few special in- 
stances, all typical proteins contain at least one representative 
from each group. 

A much more practical classification, based in part upon the 
properties of the substance, is that suggested by the Joint Com- 
mittees on Protein Nomenclature (footnote, page 269). 

" Since a chemical basis for the nomenclature of the proteins 



272 PHYSIOLOGICAL CHEMISTRY 

is at present not possible, it seems important to recommend 
a few changes in the names and definitions of generally accepted 
groups, even though, in many cases, these are not wholly satis- 
factory." The recommendations are as follows: 

First. The word proteid should be abandoned. 

Second. The word protein should designate that group of 
substances which consist, so far as is known at present, essen- 
tially of combinations of a-amino acids and their derivatives, 
e.g., a-aminoacetic acid or glycocoll; a-amino propionic acid or 
alanin; phenyl-o:- amino propionic acid or phenylalanin ; guani- 
dine-amino valerianic acid or arginine, etc., and are therefore 
essentially polypeptides. 

Third. That the following terms be used to designate the 
various groups of proteins: 

I. Simple Proteins. 

Protein substances which yield only a-amino acids or their 
derivatives on hydrolysis. 

Although no means are at present available whereby the 
chemical individuality of any protein can be established, a 
number of simple proteins have been isolated from animal and 
vegetable tissues which have been so well characterized by con- 
stancy of ultimate composition and uniformity of physical 
properties that they may be treated as chemical individuals 
until further knowledge makes it possible to characterize them 
more definitely. 

The various groups of simple proteins may be designated as 
follows : 

(a) Albumins. — Simple proteins soluble in pure water and 
coagulable by heat; e.g., ovalbumin, serum albumin, lactalbumin, 
vegetable albumins. 

(b) Globulins. — Simple proteins insoluble in pure water, but 
soluble in neutral solutions of salts of strong bases with strong 



PROTEINS 273 

acids;* e.g.,f serum globulin, ovoglobulin, edestin, amandin, and 
other vegetable globulins. 

(c) Glutelins. — Simple proteins insoluble in all neutral 
solvents but readily soluble in very dilute acids and alkalies;! 
e.g., glutenin. 

(d) Alcohol-soluble Proteins (Prolamines). — Simple proteins 
soluble in relatively strong alcohol (70 to 80 per cent), but in- 
soluble in water, absolute alcohol, and other neutral solvents;! 
e.g., zein, gliadin, hordein, and bynin. 

(e) Albuminoids. — Simple proteins which possess essentially 
the same chemical structure as the other proteins, but are 
characterized by great insolubility in all neutral solvents ;|| e.g., 
elastin, collagen, keratin. 

(J) Histones. — Soluble in water and insoluble in very dilute 
ammonia and, in the absence of ammonium salts, insoluble even 
in an excess of ammonia; yield precipitates with solutions of 
other proteins and a coagulum on heating which is easily soluble 
in very dilute acids. On hydrolysis they yield a large number 
of amino acids, among which the basic ones predominate; e.g., 
globin, thymus histone, scombrone. 

(g) Protamines. — Simpler polypeptides than the proteins in- 
cluded in the preceding groups. They are soluble in water, un- 
coagulable by heat, have the property of precipitating aqueous 
solutions of other proteins, possess strong basic properties and 

* The precipitation limits with ammonium sulphate should not be made a 
basis for distinguishing the albumins from the globulins. 

t The examples of the various proteins are those given by Prof. P. B. Hawk. 

% Such substances occur in abundance in the seeds of cereals and doubtless 
represent a well-defined natural group of simple proteins. 

§ The sub-classes defined {a, b, c, d) are exemplified by proteins obtained from 
both plants and animals. The use of appropriate prefixes will suffice to indicate 
the origin of the compounds, e.g., ovoglobulin, myoalbumin, etc. 

|| These form the principal organic constituents of the skeletal structure of 
animals and also their external covering and its appendages. This definition does 
not provide for gelatin, which is, however, an artificial derivative of collagen. 



274 PHYSIOLOGICAL CHEMISTRY 

form stable salts with strong mineral acids. They yield com- 
paratively few amino acids, among which the basic amino acids 
greatly predominate; e.g., salmine, sturine, clupeine, scombrine. 

II. Conjugated Proteins. 

Substances which contain the protein molecule united to 
some other molecule or molecules otherwise than as a salt. 

(a) Nucleo proteins. — Compounds of one or more protein 
molecules with nucleic acid; e.g., cystoglobulin, nucleolus tone. 

(b) Glycoproteins. — Compounds of the protein molecule 
with a substance or substances containing a carbohydrate group 
other than a nucleic acid; e.g., mucins and mucoids (osseomu- 
coid, tendomucoid, ichthulin, helicoprotein) . 

(c) P ho spho proteins. — Compounds of the protein molecule 
with some, as yet undefined, phosphorus-containing substance 
other than a nucleic acid or lecithins;* e.g., caseinogen, vitellin. 

(d) Hemoglobins. — Compounds of the protein molecule with 
hematin or some similar substance; e.g., hemoglobin, hemo- 
cyanin. 

(e) Lecitho proteins. — Compounds of the protein molecule 
with lecithins (lecithans, phosphatides); e.g., lecithans, phos- 
phatides. 

III. Derived Proteins. 

i. Primary Protein Derivatives. — Derivatives of the pro- 
tein molecule apparently formed through hydrolytic changes 
which involve only slight alterations of the protein molecule. 

(a) Proteans. — Insoluble products which apparently result 
from the incipient action of water, very dilute acids or enzymes; 
e.g., myosan, edestan. 

(b) Metaproteins. — Products of the further action of acids 

* The accumulated chemical evidence distinctly points to the propriety of 
classifying the phosphoproteins as conjugated compounds; i.e., they are possibly 
esters of some phosphoric acid or acids and protein. 



PROTEINS 275 

and alkalies whereby the molecule is so far altered as to form 
products soluble in very weak acids and alkalies, but insoluble 
in neutral fluids. 

This group will thus include the familiar "acid proteins" and 
" alkali proteins," not the salts of proteins with acids; e.g., acid 
metaproteins (acid albuminate), alkali metaprotein (alkali 
albuminate) . 

(c) Coagulated Proteins. — Insoluble products which result 
from (1) the action of heat on their solutions, or (2) the action 
of alcohols on the protein. 

2. Secondary Protein Derivatives* — Products of the further 
hydrolytic cleavage of the protein molecule. 

(a) Proteoses. — Soluble in water, uncoagulated by heat, and 
precipitated by saturating their solutions with ammonium sul- 
phate or zinc sulphate ;f e.g., protoproteose, deuteroproteose. 

(b) Peptones. — Soluble in water, uncoagulated by heat, but 
not precipitated by saturating their solutions with ammonium 
sulphate;J e.g., antipeptone, amphopeptone. 

(c) Peptides. — Definitely characterized combinations of two 
or more amino acids, the carboxyl group of one being united 
with the amino group of the other, with the elimination of a 
molecule of water; § e.g., dipep tides, tripep tides, tetrapep tides, 
pen tapep tides. 

Albumins. 

The albumins are conveniently represented by egg-albumin 
and serum-albumin. They are soluble in water, respond to the 

* The term secondary hydrolytic derivatives is used because the formation of the 
primary derivatives usually precedes the formation of these secondary derivatives. 

f As thus defined, this term does not strictly cover all the protein derivatives 
commonly called proteoses; e.g., heteroproteose and dysproteose. 

X In this group the kyrins may be included. For the present we believe that 
it will be helpful to retain this term as defined, reserving the expression peptide 
for the simpler compounds of definite structure, such as dipeptides, etc. 

§ The peptones are undoubtedly peptides or mixtures of peptides, the latter 
being at present used to designate those of definite structure. 



276 PHYSIOLOGICAL CHEMISTRY 

general protein reactions (Exp. 187, page 405, etc.), and may be 
completely precipitated by saturation of the solution by am- 
monium sulphate. Albumin is coagulated by heat (75 to 8o° C). 

Egg-albumin differs from serum-albumin in that it is not 
absorbed when injected into the circulation, but appears un- 
changed in the urine. Egg-albumin is readily precipitated from 
aqueous solution by alcohol, while serum-albumin is precipi- 
tated only with difficulty. Albumins in general form, with 
acids or with alkalies, derived albumins known as acid or alkali 
albumins or albuminates (acid or alkali metaproteins) . An acid 
albumin derived from myosin is known as syntonin. It differs 
but slightly from other acid albumins. The acid and alkali 
albumins are both precipitated by neutralization, but neither of 
them are coagulated by heat. 

If the hydrolysis of albumin is brought about by hydrochloric 
acid at the body temperature, it causes the molecule to split into 
two proteins, one known as antialbuminate and the other as hemi- 
albumose, these in turn becoming respectively antialbumid and 
hemipeptone. Sulphuric acid at a boiling temperature produces 
a similar change, except that the hemipeptone is further changed 
to leucin and tyrosin. Digestive ferments, pepsin, and trypsin 
produce antialbumose, hemiantipeptone, and hemialbumose, but 
trypsin alone converts the hemipeptone into leucin and tyrosin. 

Albumin normally occurs in all the body fluids except in the 
urine. The amount in milk is extremely slight; the amount in 
saliva seems to vary in inverse proportion to mucin. Albumin 
occurring in urine in appreciable quantity is always abnormal, 
although in many cases it has no serious significance unless 
persistently present in more than the slightest possible trace. 

Globulins. 

The globulins occur in both plants and animals, and crushed 
hemp seed may be used as a convenient source for laboratory 
experiment. It is also associated with albumin in blood-plasma, 



PROTEINS 277 

and may be separated from it by half saturation with ammonium 
sulphate, which precipitates the globulin only, but it is not to 
be distinguished by the ordinary protein tests and reactions. 
The albumin of albuminous urine always consists of a mixture 
of these two proteins, globulin and albumin, not, however, al- 
ways in the same proportion. The globulins are not soluble in 
distilled water as the albumins are, but a very small quantity of 
neutral salt, such as sodium chloride, will serve to effect the solu- 
tion. Globulin is thrown out of solution by action of carbon 
dioxide as a white rlocculent precipitate. By dialysis the in- 
organic salts necessary for its solution will be removed and the 
protein will be precipitated. It is also thrown out by saturation 
of sodium chloride or magnesium sulphate. Globulin is coagu- 
lated by heat at practically the same temperature as serum- 
albumin; i.e., 75 C. 

The glutelins and prolamines thus far studied have been 
mostly obtained from vegetable sources. 

Glutenin constitutes about one-half of wheat gluten, and 
the prolamines mentioned on page 273; Zein is obtained from 
maize, Hordein from barley, Gliadin from wheat or rye, and 
Bynin from malt. 

Albuminoids. 

Albuminoids are the simple proteins characterized by pro- 
nounced insolubility in al neutral salivas, and the common exam- 
ples are Keratin, from nails and hoofs, etc. ; Collagen, from bone 
and connective tissue; and Elastin, from tendons and ligaments. 

The differences in these substances are slight, the keratin 
being less soluble and less easily acted upon by digestive ferments 
than either of the other two. Keratin also contains more sul- 
phur. It is the principal constituent of horn, nails, hair, feathers, 
egg membrane, and some shells, such as turtle and tortoise. 
The sulphur content of these various sources differs considerably, 



278 PHYSIOLOGICAL CHEMISTRY 

ranging from about 5% in hair, about 3% in nail and horn, to 
1.4% in egg membrane. 

The keratins are characterized by the fact that the sulphur 
which they contain is loosely combined; i.e., easily separated by 
the formation of hydrogen sulphide and other sulphur com- 
pounds as proved by experiment No. 207. The keratins are 
insoluble in dilute acids and unaffected by any of the diges- 
tive ferments; they do, however, dissolve in the caustic alkali 
solutions, and may be used as the source of leucin, tyrosin, 
cystin, and other well-known products of protein digestion. 

Keratins heated with water, under pressure, to 150 C. will 
decompose with the formation of mercaptan, hydrogen sulphide, 
and a substance resembling the proteoses. 

Collagen, upon hydrolization with boiling water, produces 
gelatin, which is a characteristic property of this class of pro- 
teins. It may be dissolved by both the gastric and pancreatic 
juices, especially if previously treated with warm acidulated 
water. Collagen contains less sulphur than keratin and is ob- 
tained particularly from the tendo Achillis which contains about 
32% of this albuminoid and 63% of water. Collagen responds 
to the general color tests for the proteins. 

Elastin contains the least sulphur of any of the three sub- 
stances which we have considered. It may be obtained from 
the ligamentum nuchae of an ox, which contains about 31^% 
of elastin and 58% of water, by chopping the ligament finely 
and extracting for two or three days with /^//-saturated solution 
of calcium hydroxide. Like collagen, it is dissolved upon 
prolonged treatment with proteolytic ferments. 

Reticulin occurs as a fibrous part of lymph glands. It is 
insoluble in water and is not digested by pepsin or trypsin. It 
does not respond to Millon's test for proteins. 



PROTEINS 279 



Bone. 



If all organic matter is burned off from bone, there remains 
the bone-earth, so-called, made up of the phosphates and car- 
bonates of lime and magnesia, with slight amounts of chlorine, 
fluorine, and of sulphates, the proportion being practically the 
same as given for dentine, under Teeth, on page 189. Because 
in some diseases, in which the bones are softened or decalcified 
(as osteomalacia), the relation of the calcium oxide and phos- 
phorous pentoxide remains unchanged, it has been claimed that 
these substances exist in the bone in the form of a definite 
phosphate-carbonate containing three molecules of the tribasic 
phosphate to one of carbonate: 3 Ca 3 (P0 4 )2.CaC0 3 . 

If, by treatment with dilute hydrochloric acid, the mineral 
constituents are entirely dissolved out of bone, there remains 
a substance from which glue (gelatin) is derived, of similar 
composition to collagen, from connective tissue, and known as 
ossein. Neither of these (ossein or collagen) is soluble in water 
or in dilute acids. 

Bone Marrow is of two sorts, red or yellow. The red marrow 
contains erythrocytes, fat, lecithin, protein substance consisting 
of a globulin, a nucleo-protein, fibrinogen, traces of albumin and 
proteose. 

The yellow marrow is similar in composition, except that it 
contains fewer erythrocytes, more fat and more olein in the 
fat. 

Gelatin is made by hydrolysis of ossein or collagen brought 
about by prolonged boiling with dilute mineral acids. Gelatin, 
if first treated with cold water till soft, may be dissolved in hot 
water. The solution is precipitated by mercuric chloride, 
alcohol, tannic, and picric acids. It responds but feebly to the 
general protein reactions, but, by digestion with either pepsin or 
trypsin, compounds are obtained analogous to those resulting 
from similar protein digestion. 



280 PHYSIOLOGICAL CHEMISTRY 

Gelatin solutions respond to the biuret test, not to Millon's 
nor to the Hopkins-Cole test. 

Conjugated Proteins. 

These are substances which contain the protein molecule 
united to some other molecule or molecules otherwise than as a 
salt. The conjugated proteins which we shall study are mucin, 
a type of glyco-protein, yielding upon decomposition a substance 
containing a carbohydrate group; caseinogen (from milk), a 
phosphorus-containing substance; and hemoglobin (from blood). 

The glyco-protein, mucin, a selected type of this class of 
protein substance, occurs in various forms in saliva, in urine, bile, 
and other body fluids. The mucin substances are differentiated 
from the true mucins, according to Hammarsten, by the fact that 
the latter form mucilaginous or ropy solutions by the aid of a 
trace of alkali, from which they are precipitated by acetic acid. 
The precipitate is insoluble in excess of acid, or soluble only with 
great difficulty. 

True mucins have been separated and examined from the 
secretion of the submaxillary glands, from snails, from mucous 
membranes of the air passages, from synovial fluid, and from the 
navel cord. 

Mucin is quite readily converted to metaprotein by boiling 
with dilute acid, and, by action of strong acid, will yield a 
number of the simpler amino acids. Mucin itself is acid in re- 
action, but there is no evidence that it has power to form salts. 

The mucins are insoluble in pure water, but dissolve upon 
the addition of traces of alkali. The solution thus obtained will 
give the usual color reactions for the proteins. 

The action of mucin as a factor in dental caries, formation of 
gelatinous plaques, etc., will be discussed under Saliva. 

Caseinogen, the second conjugated protein which we shall 
consider, is the principal nitrogenous constituent of milk and 
will be studied as such. 



PROTEINS 281 



Milk. 



Milk is the characteristic secretion of mammals and con- 
tains the three great classes of food material, viz. : the proteins, 
carbohydrates, and fats. The fat is held as a permanent emul- 
sion in so-called milk plasma. 

The plasma consists of water holding in solution caseinogen, 
albumin with a trace of globulin, milk sugar (lactose), and mineral 
salts. 

Specific Gravity. — Milk contains two different sorts of sub- 
stances influencing the gravity; first, the fat being lighter than 
the water tends to decrease the gravity; second, the solids not 
fat which are heavier than water tend to increase the gravity of 
the milk. Consequently, it may happen that a very poor milk 
and a very rich milk will have the same specific gravity; e.g., the 
normal gravity of whole milk is about 1.031, while the gravity 
of skim milk will be about 1.035 or I -°36, and that in which cream 
occurs in large amount may be as low as 1.015 or 1.020. It can 
be easily seen that starting with whole milk, the addition of 
cream or the addition of water will both alike reduce the gravity. 
Hence, taken alone, the gravity tells little or nothing as regards 
the quality of milk; but, if the gravity is taken together with 
the fat content, the two factors give oftentimes sufficient infor- 
mation. 

The relation between the gravity of the fat and the total 
solids is approximately constant, and the following formula 
will give the amount of total solids usually within 0.10 or 0.15 
of 1%. 

Total solids _ ^X_6 + Spxgr, 
5 4 

Reaction. — The reaction of cow's milk, when perfectly 
fresh, is amphoteric to litmus; i.e., it will both redden blue litmus 
paper and turn red litmus blue at the same time. This double 



282 PHYSIOLOGICAL CHEMISTRY 

reaction is due to the presence of various salts; probably the 
acid and alkaline phosphates. 

Cow's milk is acid to phenolphthalein, and this acidity 
naturally increases by the multiplication of various acid-forming 
bacteria, which produce lactic acid by hydrolysis of the milk 
sugar. When the acid strength has increased sufficiently, the 
caseinogen is decomposed, and casein is produced and pre- 
cipitated. 

This casein constitutes the curd, and the process is the 
ordinary souring of milk. 

Lactic acid is not the only acid produced in the. spontaneous 
fermentation of milk, as traces of formic, acetic, butyric, and 
succinic acids have been demonstrated by different investiga- 
tors. 

The degree of acidity of milk is conveniently determined as 
suggested by W. Thorner (Chem. Zeit, 1891, page 1108, abst. 
analyst XVI, 200), 10 ex. of milk with an equal volume of water 
and a few drops of phenolphthalein as indicator, are titrated with 
N/10 alkali and every tenth of a degree of alkali used is con- 
sidered as representing one " degree" of acidity. 

By experimenting on samples kept under various con- 
ditions, Thorner found that milk coagulates on boiling when 
the acidity reaches 23 . Adopting 20 as the permissible limit 
of acidity, he proposes the following test: 10 c.c. of milk, 20 c.c. 
of water, a few drops of indicator, and 2 c.c. of decinormal alkali 
are thoroughly mixed; if any red color, however weak, results, 
the milk will not coagulate upon boiling.* 

This method is given partly for its own sake and partly be- 
cause exactly the same method is used by Dr. Eugene S. Talbot 
of Chicago and many others for the determination of acidity of 
urine. By slight modification it may be used for saliva. The 
record of slight amounts of acidity made in degrees in this way 
has several practical points in its favor. 

* From Allen's Commercial Organic Analysis, Vol. 4. 



PROTEINS 



283 



Casein is the principal protein found in milk. It exists in 
combination with calcium salts as caseinogen. This combina- 
tion is broken up and the casein precipitated by the action of 
rennin and other enzymes, by acids, and by certain inorganic 
salts. 

Casein is classified as a pseudo-nucleo-albumin. The nucleo- 
proteins, so named because true nuclein may be obtained from 
them, are constituents of the cell nuclei, and differ in composi- 
tion from ordinary proteins by containing from 0.5 to 1.6% of 
phosphorus. Casein from cow's milk contains, according to 
Hammarsten, 0.85% of phosphorus. It has been classified as 
a />smfo-nucleo-albumin because, upon digestion with pepsin, 
pseudo-nuclein rather than true nuclein is obtained. 

Casein is practically insoluble in water, but dissolves readily 
in dilute alkaline solutions. Its precipitation as curd is de- 
pendent upon the presence of calcium salts. 

Lactalbumin is the only other protein substance worthy of 
note in milk. This may be found in the filtrate after separat- 
ing the casein. The total proteins contained in human milk 
average from 1.5 to 2.5 per cent while in cow's mi k the proteins 
are 3.0 to 4.5 per cent. This difference, together with the vari- 
ation of reaction and sugar-content, makes it necessary to 
"modify" cow's milk when it is used as an infant food. 

The modification usually consists in the addition of lime- 
water (to change the reaction), of water (to reduce percentage of 
proteins), and of cream and milk-sugar (to increase fat and 
lactose) . 

The following table shows comparative composition: 





Reaction. 


Total 
solids. 


Proteins. 


Sugar. 


Fat. 


Ash. 


Human milk. . 
Cow's milk. . . 


Alkaline 
Acid 


13.00% 
14.00% 


2.70% 
4-15% 


6.10% 
4 90% 


4.00%) 
4-25% 


0-2D% 
0.70% 



284 PHYSIOLOGICAL CHEMISTRY 

Fat. — The fat of milk exists as microscopic globules appar- 
ently inclosed in a protein-like membrane separating substance, 
the presence of which seems a necessary theory to account for 
the behavior of milk fat toward various solvents such as ether. 
The milk fat or butter fat consists largely of olein and palmitin 
with a slight amount of butyrin and traces of several other fatty 
acids. 

Milk, as has already been stated, undergoes lactic acid 
fermentation readily and this may be induced by a considerable 

number of microorganisms. It is 
not, however, liable to alcoholic 
fermentation except under peculiar 
circumstances. Alcoholic fermen- 
tation may be induced by certain 
ferments, such as the Kephir grain 
used quite largely in the East, the 
product being known as Kumiss 
or milk wine. Kumiss originally 
was produced from mare's milk, 
Fig. 18. Milk and Colostrum. but the name has also been applied 
to any milk which has undergone alcoholic fermentation. 

Colostrum is a peculiar substance occurring at the very 
earliest stages of lactation. Its specific gravity is considerably 
higher than that of milk, being 1.040 to 1.060. It contains 
much more protein substance and is characterized by the pres- 
ence of granular corpuscles known as colostrum corpuscles. 
(Fig, 18.) 

Derived Proteins. 

Meta-proteins — Acid Meta-protein. — The digestive action 
of the gastric juice on protein substances is the formation 
of an acid meta-protein, formerly called acid albuminate. 
The meta-proteins are characterized by the fact that they 




PROTEINS 285 

are precipitated on neutralization and are not coagulated by 
heat. They may also be precipitated by saturation with com- 
mon salt. 

The Alkali Meta-protein or alkali albuminate is the stronger 
of these two classes of compounds when considered from a chem- 
ical standpoint; that is, the reactions are more marked, and some 
compounds will be formed with the alkali albuminate which are 
not produced when the acid albuminate is treated in a similar 
way. The acid meta-protein from the digestion of meat is known 
as syntonin. 

The Proteoses (albumoses) may be considered as the next 
well-defined protein product of protein digestion following the 
albuminate. That is, leaving out the many intermediate prod- 
ucts between which sharp lines of demarcation cannot be drawn, 
the decomposition of albumin brought about by enzymes or 
digestive ferments gives, first, acid albumin; second, albumose; 
and third, peptone. Albumose may be taken as a type of this 
second class of digestive products. Other proteoses, such as 
globulose, etc., are the substances derived from other proteins 
at a corresponding point of decomposition or peptic digestion. 
Albumose may be coagulated by heat at a temperature ranging 
upwards from 5 6° C, but, unlike albumin, as the temperature 
approaches the boiling-point the albumose goes again into solu- 
tion, and at a boiling temperature may be separated from albumin 
by filtration. As the filtrate cools, albumose will again precipi- 
tate. The albumose is also precipitated by nitric acid, by ferro- 
cyanide of potassium and acetic acid (the precipitate in both cases 
being dissolved by heat), and the other general protein precipi- 
tates. The biuret test gives a distinctive color with proteoses 
and peptones, it being a marked reddish shade rather than the 
violet or blue obtained with other proteins. 

Peptones are the final products of peptic digestion of the 
proteins. They are soluble substances which give the biuret 
test similarly to the proteoses, but are not precipitated by heat, 



286 PHYSIOLOGICAL CHEMISTRY 

by nitric acid, by potassium ferrocyanide and acetic acid, nor 
by saturation with ammonium sulphate. 

Peptides. — The peptides are the simpler forms of the pep- 
tones, many of them being complex amino acids. Upon decom- 
position or hydrolytic splitting of peptide, the simpler amino 
acid, which is without the protein characteristics, results. 

BLOOD AND MUSCLE. 

Blood. 

The blood, carrying oxygen and other forms of nutrition to 
all parts of the body, and returning carbon monoxide and the 
waste products of cellular activity, is an exceedingly complex 
substance. The composition of the blood itself, however, may 
be grossly described as a fluid (plasma) carrying in suspension 
the cellular constituents, red and white corpuscles. The plasma 
contains solid matter to the extent of about 8.9%. This is 
largely protein, consisting of serum globulin, serum albumin, 
a slight amount of nucleoprotein, and fibrinogen; also a fibrin 
ferment, thrombase or thrombin, by the action of which the 
fibrin is separated as a "clot" which mechanically carries down 
the corpuscles. As the clot contracts, the "serum" separates 
as a clear, amber-colored liquid, consisting of serum globulin 
(paraglobulin) , serum albumin, and the fibrin ferment. 

Fibrin. — The fibrin may be obtained free from corpuscles 
by whipping fresh blood. Under this treatment the fibrin 
separates as shreds, while the remaining fluid constitutes "de- 
fibrinated blood." The presence of lime-salts is essential to 
the coagulation of the blood, i.e., the decomposition of fibrin- 
ogen and separation of fibrin, in much the same way as in the 
decomposition of caseinogen and precipitation of casein from 
milk. 

Fibrin, as usually obtained, is in the form of brown, stringy, 
and "fibrinous" masses, which are kept under glycerin for labor- 



PLATE ML— PHYSIOLOGICAL CHEMISTRY. 





Fig. i. 

Edestin. 



Fig. 2. 
Teichmann's Hemin Crystals. 





Fig. 3. — Fat Crystals. 
A, Butter Crystals; B, Lard Crystals. 



Fig. 4. 
A, Fat Acid; B, Cholesterin. 





Fig. 5. 

A, Human Blood; B, Horse Blood; 

C, Dog Blood. 



Fig. 6. 
A, Frog Blood; B, Chicken Blood; 
C, Fish Blood. 



BLOOD AND MUSCLE 287 

atory use. It is insoluble in water or alcohol. In dilute acid, 
(HC1), or alkali solutions, it swells and ultimately dissolves, 
although it may be several days before solution is effected. The 
fibrins from the blood of different animals differ in composition, 
as indicated by marked differences in solubility. 

The chemistry of the red and white corpuscles is more complex 
and not so well known as the chemistry of the plasma, which 
we have considered. The red corpuscles consist of a frame of 
protoplasm, also called stroma, which contains lecithin, choles- 
trin, nucleoalbumin, and a globulin. (Hammarsten.) Upon 
and all through the stroma is the hemoglobin, which, together 
with its oxygen compound oxyhemoglobin, is responsible for 
the color of the blood. Oxyhemoglobin may be obtained as 
silky, transparent crystals of blood-red color. 

From hemoglobin may be derived the blood pigment hemo- 
chromogen, containing iron, and this by oxidation is converted 
into hematin. The iron from the blood may, by decomposi- 
tion of the pigment and subsequent combination with sulphur 
(FeS), cause discoloration of teeth. This is the theory of Dr. 
E. C. Kirk, and in the author's opinion is perfectly sound, and 
far more probable than other explanations which have been 
offered, but which do not recognize the formation of a sulphur 
compound. 

The form of the red corpuscle is that of a biconcave disk 
without nucleus; by action of water it becomes swollen, and 
the hemoglobin may be washed away, leaving the "stroma." 
The diameter of the red corpuscles of human blood is about 
1/3200 of an inch. Of the domestic animals, the corpuscles of 
the dog approach most nearly to the measurement of the human. 
The sheep, horse, and ox have smaller corpuscles than man, 
while those of birds, cold-blooded animals, and reptiles are 
larger (see Plate VII, Figs. 5 and 6). 

The white corpuscles are rather larger than the red, and 
occur in much smaller numbers, a cubic millimeter containing 



288 PHYSIOLOGICAL CHEMISTRY 

about 5,000,000 red to 7500 white. The white corpuscles pre- 
sent a much greater diversity of character than do the red. 
They contain one to four nuclei, and are capable of amoeboid 
movements. The white corpuscles are also called leucocytes, 
aggregations of which constitute pus. The leucocytes are di- 
vided histologically into various classes, — lymphocyte, neutro- 
phils, eosinophiles, etc., — according as they are acted upon 
by different staining-fluids or fulfill some particular office; but 
these are not to be distinguished chemically. 

Hemoglobin. — Hemoglobin may be separated from blood 
by shaking with a little ether and water and allowing to stand 
twelve hours on ice; or sometimes crystals may be obtained by 
simply allowing a drop of defibrinated blood to partially dry on 
a microscope slide. The hemoglobin from different animals 
crystallizes in more or less distinctive forms; for example, from 
human blood the crystals will be diamond shape or rectangular, 
from guinea pigs, tetrahedrons or octahedrons resembling the 
crystals of white arsenic, and from squirrels, six-sided plates. 

The composition of hemoglobin has been given as 96% 
globin (a histone), and the remainder hemochromogen. 

Hemoglobin forms compounds with various gaseous sub- 
stances and furnishes a good example for the study of the law 
of mass action. In the lungs excess of oxygen slowly drives 
other gases, particularly carbon dioxide, out of combination, 
and forms oxyhemoglobin, while in the capillaries excess of 
carbon dioxide in venous blood replaces the oxygen. Hydrogen 
sulphide, nitric oxide, nitrous oxide, and carbon monoxide all 
form compounds with hemoglobin of various degrees of stability, 
the most stable being formed by carbon monoxide which acts by 
preventing the formation of oxyhemoglobin. Blood containing 
carbon monoxide hemoglobin is of a bright-red color, which 
darkens in the air much more slowly than ordinary blood. 

Hematin is an oxidation product of hemoglobin and has 
been assigned the formula C32H32N4O4FC 



BLOOD AND MUSCLE 289 

Hemin, or Teichmann's hemin crystals, is the hydrochloric 
acid compound of hematin. (See Exp. 239, page 414, also 
Plate VII, Fig. 2.) 

Muscle. 

The chemistry of muscle is complex. It changes rapidly 
upon the death' of the animal, so much so that the liquid which 
may be expressed from living muscle (or from muscle frozen 
immediately upon the death of the animal) has been called 
muscle plasma, in distinction from the fluid obtained in the 
same manner from dead muscle, which is called muscle serum. 
The chemical reactions of these solutions differ, due to the 
formation of sarcolactic acid in the dead muscle. The proteins 
differ in certain respects. 

The two proteins of muscle plasma are given by Halliburton 
as paramyosinogen 25%, and myosinogen 75%. Of these the 
paramyosinogen seems to be a globulin, while the myosinogen, 
having many of the properties of a globulin, is soluble in pure 
water and is rather a mother protein from which the clot from 
muscle serum is produced. The protein of the muscle clot is 
known as myosin or myogen. Myosin may be precipitated from 
muscle serum by saturation with sodium chloride or magnesium 
sulphate. It has many of the properties of the globulins, but 
differs in the very important particular of not being precipitated 
by dialyzation. Among the more important extractive bodies 
obtained from muscle are creatin, carnin, inosite, glycogen, and 
lactic acid. Creatin is a xanthin body, being chemically a 
methyl-guanidin-acetic acid, which may appear in the urine as 
creatinin. (Creatinin is creatin minus water.) 

Carnin is a white crystalline substance obtained from meat 
extract and converted by oxidation induced or produced by 
nitric acid, chlorine or bromine into hypoxanthin or sarkin. Its 
chemical constitution is not positively known. 



290 PHYSIOLOGICAL CHEMISTRY 

Inosite, C 6 Hi 2 06 + H 2 0, is a hexahydroxybenzene, C 6 H 6 (OH) 6 
+ H 2 0. It has a sweet taste, and was formerly erroneously 
classed with the carbohydrates. It is capable of yielding lactic 
and butyric acids (?). 

Glycogen occurs in slight amounts in muscle, but decomposes 
after death, with formation of a reducing sugar. (Compare 
page 263.) 

Lactic Acid is a constituent not only of muscle but also of 
various glands, of the bile, and of blood. For the chemistry 
of this substance, see page 222. 



PART VII. 

DIGESTION. 

CHAPTER XXXIII. 

SALIVA PROPERTIES AND CONSTITUENTS. 

The saliva is a mixed secretion from the parotid, submaxil- 
lary, and subKngual glands," together with a slight amount 
obtained from the smaller buccal glands. The chemical com- 
position of the secretion from these various sources differs con- 
siderably, but from a dental standpoint we are much more 
interested in the mixed saliva and its constituents than the 
differences in the products of the various glands. The notable 
differences are that the mucin is practically wanting in the 
parotid saliva. The alkaline salts seem to be in smaller pro- 
portion in the parotid saliva than in the other two. Potassium 
sulphocyanate is a constituent of all varieties of saliva, although 
more constantly present in the submaxillary and in the sublingual 
than in the parotid. The parotid, on the other hand, contains 
a larger proportion of dissolved gases. The data on the com- 
position of these varieties differ to a considerable extent and 
comparisons are not wholly satisfactory. 

The mixed saliva contains, according to Professor Michaels, 
all the salts of the blood which are dialyzable through the salivary 
glands, and hence furnishes a reliable index of metabolic proc- 
esses which are being carried on within the system. In order 
for this fact to be of practical 'value, two things are obviously 
of prime importance: First, methods of analysis which are not 
too complicated and which are at the same time conclusive; 

291 



292 DIGESTION 

second, a knowledge regarding the source of the various con- 
stituents found which will enable us to make a rational inter- 
pretation of the results obtained. In both of these fundamentals 
we are very much hampered by lack of knowledge; as yet there 
is much to be desired in the way of practical clinical tests for 
the various salivary constituents, and very much to be learned 
as to their meanings in order to make deductions which shall 
be conclusive. We are led to believe from the work of an 
increasing number of specialists that this subject of salivary 
analysis promises much and is certainly worthy of careful 
investigation. 

The quantity of saliva secreted in twenty-four hours is vari- 
ously estimated from a few hundred to 1500 c.c; 1200 to 1500 
is the more probable amount. The quantity is diminished in 
fevers, severe diarrhea, diabetes, and nephritis, by fear and 
anxiety, and by the use of atropine. It is increased by smoking, 
by mastication, by the use of mercury, potassium iodide, or 
pilocarpin. The flow of saliva is also increased by action of the 
sympathetic nervous system, during pregnancy, and by local 
inflammatory process. 

Physical Properties. — The physical properties of saliva in- 
clude its appearance, specific gravity, reaction, color, and odor. 

Appearance. — The appearance is clear, opalescent, frothy, 
or cloudy; normal saliva is usually opalescent. It may become 
turbid by precipitation of lime-salts caused by the escape of 
carbon dioxide. 

Specific Gravity. — Specific gravity ranges from 1.002 to 1.009, 
the total solids being only from 0.6 to 2.5 per cent. 

Reaction. — The reaction is normally alkaline to litmus- 
paper or to lacmoid. Normal saliva, however, fails to give 
an alkaline reaction with phenolphthalein, due to the presence 
of free carbon dioxide, which may be present to the extent of 
nineteen parts in a hundred, by volume. If the sample be 
subjected to even a slight degree of heat the acid gas is expelled; 



SALIVA PROPERTIES AND CONSTITUENTS 293 

then the usual pink color may be obtained with this indicator. 
Saliva may be acid upon fasting, particularly before breakfast 
and also after much talking. Acid conditions may exist which 
are local in their character and due to lactic acid fermentation. 
Acid salivas may also be met with in cases of rheumatism, 
mercury salivation, and diabetes. By exercise of the glands, 
as during the chewing of food, the alkalinity is increased; often- 
times the reaction changes from faintly acid to alkaline during 
this process, the proportion of alkaline salts becoming greater, 
although the total solids as a whole are slightly diminished. 
This fact of the change in the reaction from acid to alkaline 
has been explained by ascribing the acidity to fermenting 
particles in the mouth; the continued process of chewing and 
swallowing washes this away, or, in other words, the change in 
reaction is a mechanical one rather than a change of the chemical 
composition of the secretion. This explanation seems to be a 
superficial one and without sufficient experimental foundation. 

The acidity of saliva, as indicated at the bottom of page 292, 
is referred to the behavior of the saliva to phenolphthalein, 
and is in large part due to the presence of free carbon 
dioxide. 

The sources of carbon dioxide in saliva are probably three: 
carbon dioxide dialyzed through the salivary glands, traces 
from carbohydrate fermentation, and more or less absorbed 
from contact with expired air. 

The saliva obtained by chewing paraffin (a process calcu- 
lated to furnish the maximum amount from the last two sources), 
may yield several times the amount of free carbon dioxide that 
another sample taken from the same patient by a saliva ejector 
will give. 

Acidity of saliva may be temporary when it may be entirely 
removed by drawing air through the heated (not boiled) sample. 
The permanent acidity may be determined by titration of the 
sample after removal of carbon dioxide. 



294 



DIGESTION 



The apparatus pictured in Fig. 19 has been used by the 
author for this acidity determination. 

The air is drawn from left to right first through a potash 
bulb (A) to absorb atmospheric carbon dioxide, next through 




10 c.c. of saliva diluted with 20 c.c. of water contained in a 
small Soxhlet flask (B) whereby the carbon dioxide from the 
saliva is carried through the " test-tube " condenser and col- 
lected in baryta water in the Erlenmeyer flask (C) at the left. 
This in turn is connected with a suction pump or aspirator. 



SALIVA PROPERTIES AND CONSTITUENTS 



295 



The " drip cup " (D) has been found necessary when working 
with very viscid samples. The thistle tube (E) holds water for 
maintaining the volume in (B) if the condenser is not used. 








Colorimeter. 



The amount of free carbon dioxide may be determined by 
adding a standard carbonate solution (N/100 Na 2 C0 3 ) to a 
volume of baryta water equal to that used in the Erlenmeyer 
flask and then comparing the degree of turbidity obtained. 
This may be done by viewing through flat-bottom tubes (shell 



296 DIGESTION 

tubes) of about 20 c.c. capacity, or, in many cases, better, by 
use of the Duboscq colorimeter used for determination of am- 
monia (Fig. 20, page 295), or better still by the use of the 
nephelometer made with the Duboscq colorimeter after the 
method of Dr. Bloor. (Journal of Biological Chemistry, vol. 
22, p. 145, 1915.) This apparatus may also be used to advan- 
tage in the determination of calcium in saliva, or acetone bodies 
in urine. The nephelometer differs from the Duboscq color- 
imeter in that it makes use of reflected rather than transmitted 
light. 

The following method for the determination of temporary 
acidity is also recommended. Force air free from carbon diox- 
ide through a measured volume of saliva (20 c.c.) which has been 
previously mixed with an equal volume of water, then into 
baryta-water containing a little barium chloride, using a Folin 
absorption tube (Fig. 25, page 310). The carbon dioxide thus 
becomes fixed as barium carbonate. Transfer the precipitated 
carbonate to a filter paper and wash free from chlorine. Dis- 
solve off paper in dilute hydrochloric acid, collecting filtrate in 
porcelain dish. Evaporate to dryness over water bath and 
titrate chlorine with N/20 silver nitrate. 1 c.c. N/20 AgN0 3 = 
.0010917 gram of C0 2 . 

Another method consists in passing carbon dioxide as above, 
into a measured volume of standardized baryta- water (N/20) 
and titrating excess of barium hydroxide with N/20 oxalic acid. 
The end point is determined by " spotting" onto fresh tumeric 
paper. When the paper ceases to turn brown-red the end of 
the reaction has been reached. 

Permanent acidity is of comparatively rare occurrence and 
is due either to the presence of acid salts, such as NaH 2 P0 4 , or 
slight amount of organic acids possibly combined as acid meta- 
protein. This acidity and its clinical significance is at present 
under investigation. 

Color. — Saliva is usually colorless when fresh, but upon 



SALIVA PROPERTIES AND CONSTITUENTS 297 

standing for twenty-four hours may assume various tints, 
which are developed from constituents derived from bile. (Pro- 
fessor Michaels.) Saliva may be colored red or brown by the 
presence of blood or blood pigments, but in such cases the 
source of the color is usually local and easily discovered. 

Odor. — Normal saliva is practically odorless. In cases of 
pyorrhea there is usually a peculiar fetid odor easily recognized. 
In other pathogenic conditions the odor may be slightly am- 
moniacal, or occasionally resemble the odor of acetone or 
garlic. 

Constituents. — We should here distinguish carefully be- 
tween saliva proper and sputum. The constituents of sputum 
are derived from the air-passages rather than from the salivary 
glands, and are not at present under consideration. Among 
the normal constituents of saliva are included mucin, albumin, 
ptyalin, also oxidizing enzymes, ammonium salts, nitrites, 
potassium sulphocyanate, alkaline phosphates, and chlorides, 
with traces of carbonates; and, in the sediment, epithelium 
cells, occasional leucocytes, and fat globules. The abnormal 
constituents wi 1 include glycogen, urea, dextrin, rarely sugar, 
cholesterin, derivatives from bile, lecithin, xanthin bodies or 
alkaline urates, acetone, lactic acid, and crystalline elements 
resulting from insufficient oxidation or perverted glandular func- 
tion. These latter are recognizable by the micropolariscope. 
Mercury and lead may also be found in saliva in cases of poison- 
ing by salts of these metals. 

Mucin. — The secretion from the parotid gland contains 
practically no mucin, but the sublingual saliva contains large 
amounts. Mucin is, according to Simon, the most important 
constituent of the saliva, not excepting ptyalin. The various 
glands contributing salivary mucin do not in all probability 
furnish just the same kind of protein; moreover, the mucin 
from different individuals seems to vary in composition and 
properties, some yielding more abundant acid decomposition 



298 DIGESTION 

products than others (see article by W. D. Miller, in Dental 
Cosmos for November, 1905), while, according to Professor 
Michaels, the mucin varies much in the same individual in 
health and disease. The changes in the characteristics of 
salivary mucin have been studied but little, and the investiga- 
tion of these changes, as indications of diathetic states, promises 
much. 

An excess of mucin in the saliva tends to an increase of 
bacterial growth, from the fact that it furnishes increased 
facilities for multiplication; it has been suggested that it may 
also give. rise to mucic acid, and thereby be a possible factor 
in tooth erosion. (Dr. G. W. Cook in Dental Review, May, 
1906, page 461.) 

Albumin. — Albumin is present in very small quantities, 
increased during mercurial ptyalism, usually in cases of pyor- 
rhea, and, according to some authorities, in various albumi- 
nurias. It may be detected by usual methods after the separa- 
tion of mucin. 

" According to Vulpian, the quantity of albumin is increased 
in the saliva of albuminurics of B right's disease. The saliva 
of a patient with parenchymatous nephritis had mucin 0.253 
and albumin 0.182 per cent. The saliva of another patient, 
with albuminuria of cardiac origin, contained mucin 0.45, 
albumin 0.145 per cent. In a healthy man there was found 
mucin 0.320, albumin 0.05 per cent. This fact has been con- 
firmed by Pouchet, who found these substances in greater 
quantities." * 

Ptyalin. — Ptyalin is the principal ferment of the saliva; it 
converts starch, by hydrolysis through the various dextrins 
(page 263), to maltose. The maltose in turn is converted into 
glucose by a second ferment, known as maltase, which exists 
in saliva in very small quantities. 

* Dr. Joseph P. Michaels. S. S. White's reprint of paper read before Inter- 
national Dental Congress, Paris, 1900. 



SALIVA PROPERTIES AND CONSTITUENTS 299 

The activity of ptyalin is greatest at a temperature of 40 C. 
Very faintly acid saliva is the best media. Neutral and faintly 
alkaline salivas are next in order. 

The amylolytic power of a given sample of saliva may be 
determined by the action on dilute starch paste. In making 
comparative tests it is essential that the conditions under which 
the ptyalin is allowed to act should be exactly the same, es- 
pecially as regards the temperature and duration of the process. 
A slight variation in the strength of the starch solution is of no 
consequence, as starch is supposed to be in excess. (See Exp. 
245 on page 416, also method on page 313.) 

Proteolytic Enzymes. — Upon incubation with certain prod- 
ucts of protein digestion (dipeptides) proteolytic action of 
saliva has been noted; whether this action is due to an enzyme 
or to bacteria is an open question. (See fifth edition of Hawk's 
Physiological Chemistry, pages 57 and 58.) 

Oxidases. — As a result of the work of Dr. C. F. MacDonald 
in the author's laboratory, the following conclusions were 
reached regarding these enzymes: 

First. That human mixed saliva contains an oxidizing 
enzyme distinct from ptyalin. 

Second. That the enzyme exhibits the properties of both 
an oxydase and a peroxydase. 

Third. That it is a product of the body (probably glandu- 
lar) metabolism and may be increased in quantity, or activity 
by mastication. 

Fourth. That it is more resistant to heat than ptyalin, but 
more easily destroyed by acids. 

Fifth. That the color obtained with a freshly prepared 1% 
solution of pyrocatechol is sufficient test for this enzyme in 
saliva. 

The test for oxidizing enzymes may be made with the pyro- 
catechol as given on page 314; also by the use of phenolphthalin 



300 DIGESTION 

(reduced phenolphthalein) . This last reagent has recently been 
rendered available by the work of Dr. H. L. Amoss, Harvard 
Medical School, who has given us a concise and simple method 
for its preparation. (Jour. Biolog. Chem., 191 2.) 

Phosphates and Carbonates. — These salts are probably pres- 
ent in both acid and neutral forms; that is, the phosphate may 
exist as Na 2 HP0 4 also as NaH 2 P0 4 , and at times both of these 
may be present at once. The acid carbonate, NaHC0 3 , is an 
undoubted constituent, while the neutral carbonate is probably 
not present at all. Chittenden says that mixed human saliva 
contains normally no sodium carbonate whatever. 

As explained by Dr. Kirk, the normal reaction by which 
overacidity of the blood is taken care of by renal epithelium 
is H 2 C0 3 + Na 2 HP0 4 = NaH 2 P0 4 + NaHC0 3 , and when con- 
ditions are such as to produce larger quantities of carbonic acid 
than the kidneys can eliminate in accordance with the above 
reaction, there is an increased acidity of the saliva as well as of 
the urine.* In the hypoacid individual, the so-called alkaline 
sodium phosphate, Na 2 HP0 4 , is present in the greater quantity. 
In diabetic patients, sugar has very rarely been found in the 
saliva; one case coming under the observation of the author 
was that of a woman of middle age, with diabetes of long stand- 
ing, with 8% of sugar in the urine, and from this case there were 
obtained a very few osazone crystals by subjecting a consider- 
able quantity of saliva, after concentration, to the phenyl- 
hydrazine test. 

Urea has been repeatedly found in the saliva of patients 
suffering from chronic nephritis. 

Acetone is of quite frequent occurrence in the saliva. In 
diabetic patients this substance is often present in compara- 
tively large amounts, sometimes sufficient for the detection of 
the acetone by its characteristic odor. Acetone may appear in 
the saliva when it is not present in the urine. In such cases it 

* International Dental Journal, February, 1904. 



SALIVA PROPERTIES AND CONSTITUENTS 301 

has usually resulted from disordered digestion and a consequent 
faulty metabolism. (For further consideration of acetone, see 
Urine.) 

Cholesterin and lecithin have been found by Professor 
Michaels in pathological saliva, and leucin has been found by 
Michaels in a case of lupus and, according to Novey, in a case 
of hysteria. 

Of the crystalline salts which may be separated by evapora- 
tion of dialyzed saliva, the sodium oxalate and the lactates and 
acid lactates of lime and magnesia are of the most importance 
and have been the most thoroughly studied. As these salts 
may likewise be separated from urine their significance will 
be studied under that head. 

Ammonium Salts. — Ammonium salts occur chiefly as chlo- 
ride, probably to some extent as sulphocyanate, and occasion- 
ally as oxalate. Professor Michaels says that ammonia must 
be considered as a more completely oxidized form of nitrogen 
than urea; hence its relative increase is observed in all diseases 
which occasion an excess of nitrogen and urea, as in tubercu- 
losis and all hypoacid diatheses. There is a decrease of am- 
monia whenever the nitrogen fails to reach the stage of oxidation 
represented by urea. This condition is accompanied by uric 
acid and other products of deficient oxidation, and characterizes 
the hyperacid state. 

While these statements are consistent with Dr. Michaels' 
conception of the hyper- and hypo-acid diatheses, the student 
is not to understand that ammonia is really an oxidation prod- 
uct, for we have already seen that it is formed by the splitting 
of protein derivatives. Characteristic crystals of ammonium 
chloride may be found by microscopical examination of the 
residue obtained by evaporating a clear drop of almost any 
saliva. (Plate VIII, Fig. 1, page 316.) 

Potassium Thiocyanate represents the salts of HCNS found 
in saliva. It occurs only in very slight traces in other body 



302 DIGESTION 

fluids, and in saliva only to the extent of o.ooi to 0.02%. Dr. 
Michaels considered the proportion of thiocyanates relative to 
the ammonia to be of importance and states that in health the 
ammonium salts and the thiocyanates are present in very 
slight amounts, and the color-tests, with Nessler's solution 
and with ferric chloride, respectively, are of about equal in- 
tensity. In the hyperacid state the sulphocyanates are in 
excess of ammonia, while in hypoacid conditions, the ammonia 
exists in the greater quantity. Sulphocyanate is detected by 
means of ferric chloride, and distinguished from meconates and 
acetates, as indicated by Exp. 247, page 417. 

As we shall see in a subsequent chapter the intensity of color 
produced by ferric chloride and thiocyanate is not necessarily 
an index of the quantity of HCNS present, hence the above 
conclusions are of questionable value. 

The sulphocyanates are normal constituents of saliva, and 
consequently always present. According to A. Mayer (Deutsch. 
arch. f. klin. med., Vol. 79, No. 394), the sulphocyanates, with- 
out doubt, result from the decomposition of proteins, and exist 
in the urine in quantities variously estimated from twenty to 
eighty milligrams per liter, while in saliva it has been estimated 
from sixty to one hundred milligrams per liter. Professor 
Ludholz of the University of Pennsylvania says that the sulpho- 
cyanates are eliminated in increased amounts in conditions 
where there is a lack of oxygen in the system, thus corrobo- 
rating statements of Professor Michaels (see Ammonia). Dr. 
Fenwick (Lancet, 1877, Vol. II, page 303) demonstrated that 
the quantity of KCNS was directly dependent upon the bile 
salts in the blood. He found an increase of the salt in liver 
disorders attended with increase of bile salts in the blood, and 
marked increase in jaundice. In gout, rheumatism, and con- 
ditions producing pyorrhea, it is also claimed to be present in 
considerable quantity. 

The sulphocyanates are usually present in more than normal 



SALIVA PROPERTIES AND CONSTITUENTS 303 

quantity in the saliva of people addicted to smoking tobacco.* 
The claim has been made for this salt that it exerts a specific 
antiseptic action toward bacteria. 

While the sulphocyanates, or, in fact, any salt in sufficient 
concentration, will have an inhibitory action on the growth of 
bacteria, it is rather doubtful if this is the particular office of 
KCyS in the saliva. 

Nitrites. — That nitrites exist in most salivas is without ques- 
tion. So far as we know at present, the nitrites are apparently 
incidental, and occur as intermediate products in the oxidation 
of ammonia to nitrates, just as they do otherwise in nature out- 
side of the animal body. 

It is not at all improbable that the proportion of nitrates is 
dependent upon activities of the oxidases. This has, in some 
cases at least, been proven to be the case, as the same sample 
of saliva has frequently given steadily diminishing quantities 
of nitrites until they have wholly disappeared in cases contain- 
ing active oxidizing enzymes. 

Nitrates occur in the saliva but so far as known are without 
clinical significance. 

* See article by Dr. J. Morgan Howe in Jour, of the Allied Societies, Vol. 4, 
p. 183. 



CHAPTER XXXIV. 
ANALYSIS OF SALIVA. 

The analysis of saliva may be taken up from two distinct 
standpoints, and considering our present lack of positive knowl- 
edge on this subject it may for a while be expedient so to study 
it. First, we will study a few tests of saliva of such a character 
that they may be made with simple apparatus, and which might 
be used by any dental practitioner with sufficient time and 
interest, to contribute to our general knowledge; secondly, 
we may study saliva by accurate laboratory methods which 
are not available for general use, but which are necessary for 
the establishment of positive data, and in fact necessary for an 
intelligent schedule of tests under division one. 

In 191 1 and for one or two years previous the National 
Association made an effort to establish uniform methods of 
salivary analysis, and it is deeply to be regretted that this 
effort was not continued until a system of examination had 
been perfected which might have become a recognized one for 
all workers along these lines. A necessity of uniform methods 
is generally recognized by other classes of chemists but as yet 
the fact remains that the dental chemist is obliged to formulate 
his own analytical schemes. 

We shall make three divisions of the methods to be used. 
Methods marked I are in part taken from Professor Michaels 
and are the simplest ones applicable to small amounts. They 
will give results of varying degrees of accuracy, but are of value 
because of the ease and rapidity with which they may be used. 

Methods marked II are retained from Dr. Ferris' report to 
the National Dental Association at its annual meeting in 191 1, 

304 



ANALYSIS OF SALIVA 305 

and reported in the Dental Cosmos for November of that same 
year, on pages 1295, etc. 

Methods marked III are those which the author believes to 
be the most accurate and the most satisfactory in exhaustive 
determinations. 

Physical properties of the saliva should first be noted. In 
method I, the color and appearance of the perfectly fresh sample 
is to be carefully compared with the appearance and color after 
standing for forty-eight hours in a small, tightly covered vial. 
The color may be yellowish, greenish, or brown, according to 
the variety of the derivative of biliverdin from which the color 
is obtained.* The general appearance may also change inde- 
pendently of any color. A saliva that is, when fresh, hypoacid 
in character, is, after forty-eight hours, usually markedly opal- 
escent and of offensive odor, while a hyperacid saliva may have 
become clear or cloudy but without odor. 

By method II, we should add to this examination a viscosity 
test which will be of value as indicating the amount of mucin, as 
probably the mucin content affects the viscosity more than any 
one constituent. 

The viscosity may be determined by use of the apparatus 
pictured in Fig. 21 (page 306). 

The essential features of the viscosimeter are a straight 
graduated tube with the constriction (C) jacketed so that the 
conditions under which a given sample will pass through the 
opening will always be under absolute control. 

The apparatus is standardized by partly rilling with dis- 
tilled water in which the bulb of a thermometer is immersed. 

The temperature of the distilled water is brought to 25 C. 
The thermometer is removed to facilitate reading and from 
5 to 10 c.c. of the liquid are allowed to run out, the time con- 
sumed being accurately determined by a stop watch. 

* Dr. Joseph P. Michaels. S. S. White's reprint of paper read before Inter- 
national Dental Congress, Paris, 1900. 



;o6 



DIGESTION 




Fig. 21. 



ANALYSIS OF SALIVA 



307 



The viscosity of saliva is determined in the same way, care 
being taken that only a perfectly clear solution is used as fine 
particles will clog the opening at C. The use of the stop cork 
as pictured in Fig. 21 is undesirable, in fact it has been found 
that straining the saliva, filtering through paper or even cen- 
trifugalizing in order to separate the solid portions will occasion 
a variation in the results obtained. The first determination 
should be carefully made and used, as repeated determinations 
result in a regular diminution of the viscosity figure due to 
mechanical changes brought about by passing the saliva through 
the very small opening at C. 

If the constriction of the graduated tube is sufficiently great, 
i.e., the opening sufficiently small, comparison may be made 
by counting drops delivered in a given time. This is not ad- 
vised, as there is much greater difficulty in 
obtaining the saliva free enough from sus- 
pended particles so as not to clog the tube. 

The inner tube should always be filled 
to the same mark in the determination as 
that used in the standardization of the 
instrument. 

The reaction may be taken in method I 
by the simple use of litmus paper. This 
test has a general value, and is sufficient to 
detect extreme conditions. Our second 
method should be a quantitative one, and 
the degree of alkalinity should be deter- 
mined by indirect titration. Add excess 
of N/100 HC1 to 10 c.c. of sample, and ti- 
trate back to yellow color with N/100 
NH4OH. Use paranitrophenol as indicator. The degree of acid- 
ity, using N/100 alkali and neutral phenolphthalein as an indi- 
cator, should be determined next. Then the reaction, after 
driving off carbon dioxide, should be ascertained. The per- 




Pyknometer. 



3 o8 



DIGESTION 




Fig. 23. 



mancnt acidity, if such exists, should be found a useful factor 

in the study of Dental Caries and may be determined by the 

apparatus pictured on page 294. 

Specific Gravity may be taken (Method I) by an ordinary 

urinometer or a specific gravity bulb 
if the quantity is sufficient, the read- 
ing to be made from beneath the sur- 
face of the liquid. If the quantity of 
the saliva is small, it may be diluted 
with an equal volume of water, and 
the last two figures multiplied by two 
will give the gravity of the undiluted 
sample, or the gravity may be taken 

by the pyknometer in which the bulb of the instrument is filled 

with saliva accurately to the mark M (Fig. 22), and then the 

reading of course on this instrument will 

be from the bottom up, and the lower the 

bulb sinks the greater will be the gravity 

of the sample. This method, devised by 

S. A. De Santos Saxe, M. D., for use in 

examination of urine, has been suggested 

by Dr. Ferris and adopted by the National 

Dental Association as an official method. 
For very accurate work the use of spe- 
cific gravity bottles is recommended. These 

may be obtained holding one, two, and 

five cubic centimeters (Fig. 23), and with 

an accurate balance of course the gravity 

can be accurately obtained. 
Thiocyanate (Sulphocyanate) Tests. — 

(Method I.) To a large drop of saliva 

on a white porcelain surface, add about 

half as much 5% ferric chloride, acidified with hydrochloric 

acid. A reddish coloration indicates the presence of thiocya- 






FlG. 



B 

24. — Sulphocyanate 
Tubes. 



ANALYSIS OF SALIVA 309 

nate. " (Method II.) Use a colorimetric scale (Ferris and 
Schradieck), place 1 c.c. of the specimen in tube A; 1 c.c. of 
1/2000 ammonia sulphocyanate in tube B (Fig. 24); add two 
drops of a 5% ferric chloride solution to each tube, add aqua 
distillata in tube B, until its color matches that of the specimen. 
Read the scale in thousandths and ten thousandths. 

" Care must be taken to have the bottom of the meniscus 
on the line. If these tubes are introduced in the color- 
imeter, the readings can be made more accurately. If, later, 
diacetic acid ester or other substances giving similar color 
with ferric chloride are found, a correction is made in the find- 
ing." 

With an excess of ferric chloride this test gives an idea of 
whether the amount of thiocyanate is much or little, but the 
careful dilution of a sample and comparison with standard has 
been found to be practically valueless for small amounts, which 
fact may be explained by the following experiment. 

If ferric chloride and potassium thiocyanate are mixed in 
molar proportions and diluted one to one thousand with dis- 
tilled water a solution results which is within the lower limits 
of the thiocyanate content of the saliva, but it also happens 
that ferric thiocyanate of this strength dissociates so that 10 c.c. 
in a 25 c.c. cylinder will have only a very pale straw color (the 
undissociated Fe(CNS) 3 only is red). 

If a drop of FeCl3 solution (M/i) is added the reddish color 
is restored, the ferric chloride being in excess, but the addition 
of 5 c.c. of saliva containing the average amount of thiocyanate 
instead of increasing the color on account of the additional 
Fe(CNS)3 produced, causes the color to become much paler 
than if 5 c.c. of distilled water had been added. The explana- 
tion is obvious. The total amount of ferric thiocyanate pro- 
duced, while still within the limits of the salivary content, is 
not concentrated enough but what the proportion of ionized 
salt is still in excess, and further the added saliva has con- 



3io 



DIGESTION 



tributed a certain amount of KC1 which will reduce the color 
by inducing the reverse reaction. 

3 KC1 + Fe(CNS) 3 = FeCt + 3 KCNS. 

Addition of either the acid or alkaline sodium phosphates 
(both probable constituents of saliva) will also decrease the 
intensity of the color, so in order to make accurate 
comparisons of very dilute solutions it is necessary to 
know the amounts of ionizable salts in the sample, 
which is impracticable. 

Ammonium Salts. — (Method I.) To a drop of 
saliva add one drop of Nessler's reagent: a yellow 
to brown color shows the presence of ammonium salts. 
If a precipitate forms by the addition of Nessler's 
reagent, it indicates either a large amount of ammo- 
nia or the presence of urobilin. If due to urobilin 
the precipitate is of a rose color after desiccation. 
Ammonium salts are usually seen in the evaporated 
drop examined by polarized light. (Plate VIII, Fig. 1 .) 
(Method III.) A modification of Dr. Folin's am- 
monia test in urine, using the Duboscq colorimeter. 
Measure out 10 c.c. of saliva in a large Jena test- 
tube. Add 2 c.c. of a solution containing (a) potas- 
sium oxalate, (b) potassium carbonate (15% of each). 
By means of an air current, drive the ammonia through 
a Folin absorption-tube (Fig. 25) into a 100 c.c. wide- 
mouth bottle containing 2 c.c. N/10 HC1, and about 30 c.c. water. 
In twenty minutes, all the ammonia should have gone over. 

Remove the delivery-tube, rinsing it with water, and transfer 
contents of bottle to 100 c.c. measuring flask, rinsing with 
sufficient water to make total volume about 60 c.c. 

Pipette out 1 c.c. of standard ammonium sulphate into an- 
other 100 c.c. measuring flask and dilute with water to about 
60 c.c. 




Fig. 25. 



ANALYSIS OF SALIVA 311 

Nesslerize both solutions simultaneously in the following 
manner. Provide two small beakers (100 c.c.) and place from 
10 to 15 c.c. of distilled water in each. Add to each 5 c.c. of 
Nessler's reagent. Mix the reagent with water, and add im- 
mediately to the ammonia solutions. Add about one- third of 
the diluted Nessler reagent at a time, and shake after each 
addition. 

Fill both flasks up to mark with distilled water, mix and 
compare the colors by means of a Duboscq colorimeter (Fig. 20, 
page 295). 

Urea. — Reagent, sodium hypobromite as used for urea in 
urine analysis (Appendix, page 427). 

Fill the tube of a Ferris modified Doremus ureometer with a 
saturated salt solution. Close the stopper, and add 1 c.c. of 
saliva to the upper tube. Allow this to run through the stopper 
carefully, then close, and add 1 c.c. of the reagent. When this 
has gone through, close the stopper quickly, set up the appa- 
ratus, and allow to stand one hour or longer. Then, by gently 
tapping, cause any bubbles adhering to the sides of the tube 
to rise to the top, and read the amount of gas collected. Each 
division represents 0.025. 

Chlorides. — (Method I.) To a drop of saliva add a small 
drop of a 5% solution of neutral chromate of potassium, K 2 Cr0 4 . 
Mix with a glass rod and add one drop of a 1/10% solution of 
silver nitrate. This constitutes the test for chlorine, which, 
if present in normal quantities, will give a reddish precipitate, 
gradually becoming white. Should the precipitate remain red 
it shows the chlorine deficient or less than normal in amount. 
If the precipitate rapidly turns white, or if a white precipitate 
is formed to the exclusion of the red, chlorine is increased in 
amount. High chlorine is indicative of hypoacid diathesis. 

(Method II.) To 1 c.c. of the specimen add 4 c.c. of distilled 
water and two or three drops of potassium chromate; then 
titrate with N/40 silver nitrate solution, until the first appear- 



312 DIGESTION 

ance of a permanent reddish tinge. Multiply the number of 
cubic centimeters of nitrate used by 0.0886 to find the amount 
of chlorine in 100 c.c. of saliva. 

(Method III.) Proceed as in Method II except that it is 
recommended to use 5 c.c. of the specimen and N/20 silver 
nitrate solution. Then the number of cubic centimeters of 
silver solution used multiplied by 0.00177 will give the weight 
of chlorine in the 5 c.c. of saliva taken. This times twenty 
will give the amount in 100 c.c. or the per cent. 

Glycogen. — (Method I.) A drop of saliva may be tested 
for glycogen by the addition of one drop of an aqueous solution 
of iodine and potassium iodide. This must be left for some 
time, as the test is not obtained until the drop is dried; then, 
if the color is a feeble violet around the edge, glycogen is indi- 
cated. Ii the color is a strong brown-red it indicates erythro- 
dexterin, if gray or black a reducing sugar. 

Phosphates. — The phosphates in saliva are determined as 
in urine except that it is necessary to modify the process slightly 
as given on page 340. 

Calcium may be determined by the following volumetric 
method recommended by Dr. Percy R. Howe, Dental Cosmos, 
April, 191 2. To 5 c.c. of saliva, add as much more distilled 
water and a slight excess of oxalic acid or ammonium oxalate 
(5 c.c. of normal solution will be sufficient). Add ammonium 
water to alkaline reaction, heat nearly to the boiling-point, 
and allow to stand for 20 to 30 minutes. Filter through a 
hardened filter paper into a small beaker which is allowed to 
stand on a piece of black glazed paper. Under these circum- 
stances, a slight rotary motion of the beaker will show if any 
of the white precipitate of calcium oxalate is passing through 
the paper. 

After filtration is complete, wash five times in hot distilled 
water; then place the precipitate, together with the paper, into 
a small beaker, add about 30 c.c. of dilute sulphuric acid, and 



ANALYSIS OF SALIVA 313 

heat nearly to the boiling-point; then titrate with N/20 per- 
manganate solution. 

Acetone. — (Methods I and III.) In the fifth drop dissolve 
a small crystal of potassium carbonate, then add a drop of 
Gram's reagent, when a marked odor of iodoform will indicate 
the presence of acetone. Should this odor be obtained, it is 
better to repeat this test upon a microscope slide, and examine 
carefully for the characteristic hexagonal crystals of iodoform 
(Plate V, Fig. 1, page 204). 

Nitrites. — (Method I.) Nitrites may be detected by add- 
ing to a large drop of saliva on porcelain a few drops of freshly 
prepared reagent, made by dissolving a very little naphthyl- 
amine chloride and an equal amount of sulphanilic acid in 
distilled water strongly acidulated with acetic acid. A purple 
coloration is a test for nitrates. 

This method could be made quantitative in a manner simi- 
lar to the colorimetric methods for ammonia, or thiocyanate 
of potassium; but, at the time of the present writing, there 
seems to be no particular reason for this amount of work. 

Amylolytic Enzymes. — (Method II.)* Preparation of starch 
paste. Put 15 c.c. of distilled water to boil. Meanwhile, weigh 
out three grams sterile starch and mix with 6 c.c. cold distilled 
water. Add drop by drop under constant stirring to the boiling 
water, then rinse out with 5 c.c. of distilled water any particles 
of starch adhering to the dish and add to the boiling starch 
solution. Boil one minute under constant stirring. Cool to 
blood temperature and add gradually 4 c.c. of N/100 iodine 
solution. 

This makes 30 c.c. of a 10% starch solution, which, when 
colored, is of a dark blue, and can be kept several days in the 
ice-box. 

Filling the Tubes. — Suck up the paste into glass tubes of 
1.5 mm. diameter, and cool in the ice-box. Just before using, 

* Method II as usual by Dr. Ferris (see page 304). 



314 DIGESTION 

make a file mark i cm. from the end of the tube and break off 
the piece of tubing so that it is full of the blue starch paste. 
Be sure that this small tube is broken so as to leave each end 
square and full of paste. Examine under low-power microscope. 

Determination of Enzyme. — Immediately after delivery of 
the specimen, measure 2 c.c. of saliva into a test-tube. Place 
it in the small tube of starch paste, and heat the whole in a 
thermostat at from 37 to 38 C. for half an hour. The enzyme 
of the saliva will dissolve the paste from the ends of the tube, 
leaving a blue column of paste unchanged in the center of the 
glass tube. After half an hour, measure with a micrometer 
gauge the total length of the tube and the length of the blue 
starch paste column remaining undissolved. The difference 
between these two measurements represents the amount of 
starch digested by the enzyme. Since the quantity of ferment 
in any fluid varies with the square of the length of the column 
digested, the quantity of ferment in the saliva is found by 
squaring this difference. Multiply by 100 to give the enzymic 
index. 

Oxidizing Enzyme. — (Oxydase.) Methods I and III con- 
sist of treating 5 c.c. of saliva, diluted with an equal volume of 
water, with about 1 c.c. of a 1% solution of pyrocatechol. The 
color obtained is a characteristic brown, developing within 
thirty minutes. 

Mucin and Albumin. — (Method I.) Mucin may be sepa- 
rated after taking the gravity by the addition of a little acetic 
acid. It should then be filtered off, but it will be necessary to 
dilute and agitate, in order that a fairly clear filtrate may be 
obtained. 

Albumin may be demonstrated in the filtrate, from which 
mucin has been separated by underlaying with strong nitric 
acid. This is Heller's test for albumin in the urine, and is best 
performed in a small wine-glass with round bottom and plain 
sides. 



ANALYSIS OF SALIVA 315 

Total Solids and Ash. — (Method II.) These should be de- 
termined immediately upon the arrival of the specimen to avoid 
error through evaporation of moisture. 

Use a platinum or fused silica dish of constant weight which 
has been kept in a desiccator over sulphuric acid. Weigh the 
dish accurately and rapidly, then introduce 2 J c.c. of the well- 
mixed specimen and heat in a drying oven, not over ioo° C, 
for two hours. Then place in the desiccator over sulphuric acid 
for twelve hours or longer, and weigh accurately and rapidly. 

The difference between these weights represents the weight 
of total solids. To calculate the percentage, divide by two and 
one-half times the specific gravity. 

Add to the dish two or three drops of fuming nitric acid, 
and heat over a flame, keeping the dish two inches above the 
top of the flame, until the black color has become white. Heat 
in the direct flame until glowing, place at once in desiccator to 
cool for one or more hours, and weigh. Calculate the percent- 
age of ash in same manner as of total solids. 

(Method III.) Total solids and ash are best obtained as 
follows: evaporate over a water bath five grams of the sample 
thoroughly mixed with a weighed amount (half a gram) of 
ignited magnesium oxide. The weight of residue (less the 
magnesia) obtained by drying at ioo° C, gives the total solids. 
These may be ignited until white ash is obtained and again 
weighed. The second weight (less magnesia) gives the ash. 

The use of the magnesium oxide serves to retain carbonates 
and chlorides in the total solids and the chlorides in the ash. 
It also obviates the necessity of oxidation with nitric acid, which 
would decompose many of the inorganic constituents of the ash. 

To determine weight of sediment obtain total solids as 
above; then if a portion of the saliva is carefully filtered and 
the solids determined in the clear filtrate by the same method, 
the difference between the two determinations of solids will be 
the weight of sediment, epithelium, leucocytes, etc. 



316 



DIGESTION 



Crystals from the Dialyzed Saliva. 

To obtain characteristic crystals, as has been explained in 
considering the subject of micro-chemistry, uniformity as to 
conditions under which the crystallization takes place is a 
necessity. In the case of saliva, however, we are not producing 

new compounds, but simply search- 
ing for compounds already formed 
and existing in unknown proportions 
in the samples tested. It is therefore 
necessary to make several prepara- 
tions of each sample, in order that 
we may obtain the widest range of 
possibility for characteristic crystal- 
lizations. The following method of 
procedure will usually give satisfac- 
tory results: For a dialyzer use a 
fairly wide glass tube, over one end 
of which has been tightly tied a piece 
of parchment (Fig. 26), or, better, a small dialyzing tube 
made entirely of parchment. Place about 15 c.c. of saliva 
in the dialyzing tube, and suspend it in a small beaker 
or wine-glass which contains an equal volume of distilled 
water. At the end of twenty-four hours the distilled water 
will contain the dialyzable salts in nearly the same con- 
centration as existed in the original saliva. Take four previ- 
ously prepared cell-slides (microscope slides on which a ring of 
Bell's or other microscopical cement has been placed) and fill 
each cell full of the dialyzed saliva. Put number one in a warm 
place that it may evaporate rapidly, leave number two exposed 
to the air at the room temperature and it will dry in from half 
to three-quarters of an hour. Place number three under a 
large beaker, or small bell-jar, and cover number four -with a 
cover-glass, and from time to time examine the crystals that 




PLATE VIII.— ANALYSIS OF SALIVA. 




Fig. i. 
Ammonium Chloride. 




Fig. 3. 
A, Magnesium Lactate (P. L.). 
B, Calcium Lactate (P. L.). 





Fig. 2. 
Sodium Chloride, \%. 




Fig. 4. 
A, Magnesium Acid Lactate. 
B, Calcium Acid Lactate. 




Fig. 5. 
Potassium Chloride, \% Solution. 



Fig. 6. 
Potassium Chloride, \% Solution. 



ANALYSIS OF SALIVA 317 

may be formed. Numbers three and four will probably take 
several hours, perhaps several days, before crystallization is 
complete. When the crystals have appeared, the preparation 
may be preserved by mounting in xylol balsam. In attempt- 
ing to obtain crystals from the saliva before dialyzation, results 
are usually unsatisfactory, owing to the presence of mucin 
and other organic substances which interfere with the crystal- 
lization. The crystals obtained by this method are principally 
sodium oxalate, lactates, and acid lactates of lime and magnesia, 
and rarely urates of the alkalis. (For forms of these crystals 
see Plate VIII, Figs. 3 and 4, and Plate II, Fig. 4, pages 316 
and 170.) 

Tests for Abnormal Constituents. 

Acetone, glycogen, and dextrin have already been considered. 
Urea may be demonstrated as follows: To a given volume 
of saliva add twice as much alcohol. This serves to precipi- 
tate proteins. Filter and evaporate on a water-bath till original 
volume is reached, or evaporate to less than original volume, 
and make up with distilled water. Then determine urea by 
method suggested by Dr. Ferris and given on page 311. 

Lactic, butyric, and acetic acids may each be tested for, quali- 
tatively, by the methods given under gastric digestion (q.v.). 

Mercury. — A very delicate test may be made for this metal 
as follows: Collect as large a sample of saliva as possible, dilute 
with an equal volume of water, acidify with a few drops of 
hydrochloric acid, throw in a few very small pieces of copper- 
turnings, which have been recently cleaned in dilute nitric acid, 
and boil for at least one-half hour, keeping up the volume by 
occasional additions of water. Remove the copper-filings, dry 
thoroughly on filter-paper, and place in a large-sized watch- 
glass (3 inches). In another watch-glass of similar size place 
one drop of solution of gold chloride, and quickly invert so that 
the drop remains hanging on the under side of the glass. Now 



318 DIGESTION 

place this watch-glass directly over the one containing the 
copper, so that the chloride of gold shall be suspended directly 
above the turnings and perhaps a half inch from them, then 
gently heat the lower watch-glass with a very small flame, 
when the slightest trace of mercury, which may have been 
deposited upon the copper, will be volatilized, reducing the 
chloride of gold, and causing a purplish ring to appear around 
the edge of the drop. If no reduction of the gold occurs, mer- 
cury is absent. 

Lead, which occasionally occurs in saliva, may be detected 
by the methods given under urine. 

Microscopical examination of the sediment should be made 
in every instance. Normal saliva will contain epithelium from 
various parts of the oral cavity, an occasional leucocyte, and 
occasional mold fungi, leptothrix, etc. Constituents, which per- 
haps are not properly classed as normal and at the same time 
are not pathological, are fat globules, a rare blood-corpuscle, 
sarcinae, extraneous material as food particles, starch granules, 
muscle fibers, etc. An excessive amount of blood, fat, pus, or 
micro-organisms would, of course, indicate pathogenic con- 
ditions. The bacteriological investigation of samples of saliva 
is always of interest, and may be necessary, but the detailed 
methods of such investigation do not lie within the scope of 
this work. 






CHAPTER XXXV, 
GASTRIC DIGESTION. 

Digestion begins with the action of the saliva upon the 
carbohydrates, and if mastication is sufficiently prolonged, the 
ptyalin may convert an appreciable quantity of starchy food 
into a more soluble form before it reaches the stomach. In the 
stomach the amylolitic action of the saliva is stopped by the 
contact with the gastric juice. A certain amount, however, of 
salivary digestion takes place within the stomach, due to the 
fact that considerable time necessarily elapses before the acid 
of the gastric juice has been secreted in sufficient quantity to 
completely permeate and acidify the mass of food received 
from the esophagus. As has been previously shown, a very 
feeble degree of acidity is conducive to the activity of the 
amylolytic ferment. The average alkalinity of the saliva, cal- 
culated as Na 2 C0 3 , is about 0.15 of one per cent. 

The first step in the gastric digestion is probably the union 
of the stomach hydrochloric acid with the proteins, forming 
acid albumins (metaproteins) or allied bodies which are changed 
by pepsin, which is the active digestive ferment of the stomach, 
into the proteoses, and slight amounts of the various peptones, 
following practically the changes produced experimentally on 
page 418. 

Pepsin is an active proteolytic enzyme occurring in the cells 
of the stomach-wall as pepsinogen; this latter is decomposed by 
the hydrochloric acid with the formation of free pepsin. Pepsin 
works only in faintly acid solutions, and in the stomach carries 
the digestion of proteins but little beyond the stage of the 
proteoses. 

319 



320 DIGESTION 

Hydrochloric acid is obtained from the fundus glands by an 
interchange of radicals between alkaline chlorides and the car- 
bonates of the blood.* The quantity present varies from 
nothing to 0.3%, the degree of acidity most favorable for peptic 
activity being about 0.18%. 

Aside from HC1, various organic acids may be present in 
the stomach contents; lactic acid, butyric acid, and acetic acid 
are the most important of this class, tests for which are referred 
to under analysis of gastric contents, page 417. 

Hydrochloric acid combines with protein substances of the 
food, forming a rather unstable compound in which condition 
the acid is known as combined hydrochloric acid in distinction 
from the free hydrochloric acid which the gastric juice may also 
contain. The combined acid possesses only in modified form 
the properties of the free acid, and hence is less liable to stop 
the digestive action of ptyalin from the saliva. 

Rennin is a second enzyme found in the stomach. This, like 
pepsin, also exists as a zymogen, and is liberated or developed 
by the presence of acid. Its action is particularly the curdling 
of milk, i.e., the decomposition of caseinogen (Exp. 253), and 
consequent coagulation of the casein. 

This process involves a splitting of the caseinogen into a 
slight amount of a peptone-like body and soluble casein. From 
this latter substance the insoluble curd is produced by the 
action of the calcium salts contained in the milk. Gastric 
lipase, or stomach steapsin, a fat-splitting enzyme, is a third 
enzyme, existing in the stomach in very small quantities, the 
action of which is comparatively weak and of but slight 
importance. 

It is to be noted that the digestive action of the stomach 
is only partial, the proteins being split into proteoses and to 
some extent into peptones, while further action is left for the 
more active ferments of the pancreatic and intestinal juices. 
* Long's Physiological Chemistry. 



CHAPTER XXXVI. 
PANCREATIC DIGESTION AND BILE. 

It may be an aid, in remembering the various digestive fer- 
ments, to note that in the saliva we have one principal ferment, 
ptyalin; in the stomach we have two, pepsin and rennin; in 
the pancreatic juice, three, trypsin, amylopsin, and steapsin. 
In addition to these the pancreatic juice contains a ferment 
similar to rennin known as chymosin. 

Trypsin is the proteolytic enzyme of the pancreatic juice. 
It is a much more energetic digestive agent than pepsin, con- 
verting the proteoses into peptones, tyrosin, leucin, and other 
amino acids. It also differs from pepsin in that it acts in an 
alkaline medium rather than an acid. Trypsin exists, like 
other proteolytic enzymes, as a parent enzyme, trypsinogen, 
which in itself is not a digestive ferment, but which is rendered 
active (activated) by another substance known as enterokinase. 

The enterokinase occurs in the intestinal juice, and seems to 
be secreted only as it is needed for the activation of the tryp- 
sinogen. Enterokinase does not in itself possess digestive 
power, but its action is destroyed by heat and in this it resembles 
the enzymes. 

Amylopsin, or pancreatic amylase, is the starch-digesting 
enzyme of the pancreatic juice. Here, again, we have an 
enzyme much more energetic in its action upon carbohydrates 
than the ptyalin of the saliva. It converts starch into maltose 
and to some extent to dextrin. The amylopsin is active in 
faintly alkaline or very faintly acid solution; more acid, how- 
ever, retards its action. 

The starch-splitting enzyme of the pancreas is dependent 

321 




322 DIGESTION 

upon the presence of electrolytes; if these are removed by 
dialysis a juice results which is devoid of starch-splitting power. 
A halogen ion, chlorine or bromine, is apparently essential to 
the activity of this enzyme.* 

Steapsin, lipase, is the fat-splitting enzyme of the pancreatic 
juice, inactive until it comes in contact with constituents of 
the bile. It splits the fat, as indicated on page 266, into glycerol 
and fatty acids, and also acts as an emulsifying agent. The 
free fatty acids thus formed unite with the alkaline bases found 
in the intestines to form soaps, which are also active emulsifying 
agents. 

Chymosin, or pancreatic rennin, has practically the same 
action upon caseinogen as the gastric rennin. 

The pancreatic juice and the bile enter the duodenum in 
very close proximity, and the digestive action of each is depend- 
ent, to a considerable extent, upon the presence of the other. 

Bile. — A secretion produced by the liver and stored in . the 
gall-bladder, from which it is delivered to the intestines, where 
it aids materially in emulsification and absorption of the fats. 

Composition of Bile. — The composition of bile is very com- 
plex as it contains a portion of the waste products of metabo- 
lism as well as substances playing an important part in digestion 
and designed to be reabsorbed into the circulation. 

Among the first class are the two principal bile pigments: 
the bilirubin (bile red) and its oxidation product biliverdin, 
(bile green). The bile-pigments are derived from the coloring 
matter of the blood. The appearance of either of these or of 
their derivatives, in either urine or saliva, is indicative of patho- 
logical conditions either of the liver- or bile-ducts, causing 
obstructions to the outflow of the bile or a destruction of the 
red-blood corpuscles.t The blood pigments, according to 

* Journal of the American Chemical Society, vol. 32, p. 1087, Kendall and 
Sherman, 
t Ogden. 



PANCREATIC DIGESTION AND BILE 323 

Michaels, are easily demonstrable in the desiccated saliva by 
means of polarized light. 

Cholesterol, (C27H45OH?), may also be considered a waste 
product of the bile. It is excreted with the feces; when re- 
tained it is likely to produce " gall stones " which are often 
found to consist of fairly pure cholesterol with a little coloring 
matter. 

Cholesterol, as its name implies, is an alcohol containing one 
hydroxyl group and one pair of double-bonded carbon atoms. 
It is soluble in hot alcohol from which it may be crystallized 
as thin, colorless plates. (See Plate VII, Fig. 4.) 

Two important acids of the bile are taurocholic and glyco- 
cholic, existing principally as sodium or potassium salts. Gly- 
cocholic acid upon hydrolysis splits into a simpler acid (cholic) 
and glycocoll, glycocoll being an amino-acetic acid (page 225), 
which is undoubtedly an antecedent of urea. 

Taurocholic acid, on the other hand, splits into cholic acid 
and taurine, taurine being an amino-ethyl sulphonic acid (page 

232)- 

The Intestinal Juice contains a number of substances play- 
ing an important part in the preparation of food material for 
assimilation. Among them is erepsin (erepase). This is a 
protein-splitting enzyme acting upon the products of tryptic 
digestion. It has little power upon the simple proteins, but 
will split the peptones into amino acids. There are also in the 
intestinal juice certain amylolytic enzymes, sucrase, lactase, and 
maltase which continue the digestive action started by amyl- 
opsin or by ptyalin of the saliva. 

The intestinal juice contains proteolytic enzymes which will 
hydrolyze the nucleic acids left undigested by other enzymes 
of the stomach and pancreatic juice. (See Exp. 261 page 421.) 

Secretin, excreted by the mucous membrane of the intestine, 
is a substance differing materially from the digestive ferments 
in that it is not destroyed by heat. It acts not as an activator 



324 DIGESTION 

in the sense that it starts specific chemical action, but as an 
essential constituent for the secretion of the various digestive 
fluids; i.e., the secretin in the blood starts the flow of pancre- 
atic juice, for instance, which contains the parent enzyme, 
trypsinogen, which in turn requires the action of enterokinase 
before it is in condition to perform its work of digestion. Some 
authorities claim that the secretin itself exists as a pro-secretin, 
from which it is liberated by action of acid. 









PANCREATIC DIGESTION AND BILE 



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PART VIII. 

URINE. 

CHAPTER XXXVII. 

PHYSICAL PROPERTIES OF URINE. 

Urine is a solution of waste products from the blood. It 
contains, normally, certain coloring matter, urea, uric acid in 
combination with alkaline bases, various organic constituents 
in slight amounts, including, perhaps, albumin and sugar, 
chloride of sodium, sulphates and phosphates of the alkalis and 
the alkaline earths. Abnormally the urine may contain albu- 
min, sugar, uric acid as such, bile, salts of the heavy metals, 
lead, mercury, and arsenic; occasionally albumose, peptones, 
lactates, acid lactates, oxalates, carbonates, hippuric acid, also 
organic compounds, resulting from insufficient or imperfect 
oxidations, as amino acids, leucin, tyrosin, and acetone bodies. 

We are to study the urine, not primarily with a view to the 
diagnosis of renal disease, which is more particularly the prov- 
ince of the physician, but to detect irregularities or deficiencies 
in the body metabolism, and, as far as possible, we are to study 
the methods whereby we may correct and regulate the mal- 
nutrition which lies at the foundation of many diseases of the 
oral cavity. As has been previously stated by the author,* 
if there are diseases of the oral cavity which may have their 
etiology in some systemic derangement not easily apparent, 
and if such diseases are to receive the attention of the dentist, 
he should obtain all possible light on every case, and at present 
a quantitative analysis of the urine is of greater value than 

* International Dental Journal, January, 1905. 
326 



PHYSICAL PROPERTIES OF URINE 327 

any other laboratory aid. In examining a sample of urine to 
obtain information as above indicated, it is essential that the 
sample be a portion of the mixed twenty-four-hour quantity, 
and that the total amount of the twenty-four-hour excretion 
be known. In collecting samples for such analysis a conven- 
ient method is to give the patient a one- or two-dram vial, 
nearly filled with water, and containing three or four drops of 
a commercial formaldehyde solution, with instructions to empty 
this into a bottle, or other receptacle, in which the twenty- 
four-hour sample is collected. Formaldehyde if used in this 
amount has no effect on the subsequent analysis and is a suffi- 
cient preservative. 

Physical Properties. 

Quantity. — The quantity of urine passed in twenty-four 
hours normally is about 1200 to 1400 c.c. for an adult female 
and 100 or 200 c.c. more than this for the male. The amount 
is increased in Bright's disease, in diabetes, and various other 
pathological conditions, also in cold weather when less mois- 
ture is given off from the skin. Normally, the quantity passed 
during twelve day hours, as 8 a.m. to 8 p.m., will exceed the 
amount overnight from 8 p.m. to 8 a.m. In cases of chronic 
interstitial nephritis the twelve-hour night quantity exceeds the 
day, hence it is desirable in collecting a twenty-four-hour sample 
to divide the time as suggested, and measure the amounts 
separately, especially if there is any suspicion of any chronic 
kidney disease. A diminished quantity of urine may indicate 
simply a diminished amount of water taken into the system. 
The urine is diminished pathologically in acute conditions, 
such as fevers, etc., but such samples rarely reach the dental 
practitioner. 

Color. — The normal color of the urine is usually given as 
straw color or pale yellow. If lighter than this the color is 
regarded as pale, if darker than normal it is regarded as high. 



32S URINE 

The urine may also be colored by various abnormal constitu- 
ents; it may be bright red from the presence of blood, or 
chocolate colored with a so-called coffee-ground sediment from 
decomposed-blood coloring matter. It may be brown to yel- 
low, bright blue or green, due to the ingestion of various drugs. 
If bile is present in any quantity in the urine it will have a 
dark or smoky appearance, and, upon shaking, the foam will 
have a distinctly yellowish or yellowish-green tint. 

Appearance. — In addition to the colors mentioned above 
urine may sometimes have a smoky appearance, due to the 
presence of hematoporphyrin or iron-free hematin, often found 
in cases of lead-poisoning. It may have a milky appearance, 
due to presence of finely divided fat globules, as in chylous 
urine, due to parasitic disease of the blood. It may be cloudy 
from four principal causes: first, amorphous urates; second, 
amorphous phosphates; third, pus; and fourth, bacteria. 
These may easily be distinguished. The application of a slight 
degree of heat (insufficient to cause coagulation of albumin) 
will redissolve the urates, and clear a urine which is cloudy 
from this cause. A deposit of phosphates is increased by the 
application of heat, but clears easily upon the addition of a 
few drops of acetic acid. A urine cloudy from the presence 
of pus is not cleared by either of these methods, but the cloud 
settles with comparative rapidity and pus corpuscles are easily 
recognized by microscopical examination of the sediment. If 
bacteria are present in sufficient quantity to cause cloudiness, 
the sample is apt to be alkaline in reaction and will not clear 
upon filtering. If it is necessary to obtain a clear solution, a 
little magnesium mixture may be added to the urine, then a 
little sodium phosphate; warm gently with agitation, when 
the precipitated ammonium magnesium phosphate will me- 
chanically carry down the bacteria, and a filtrate may be ob- 
tained which, after acidifying with dilute acetic acid, will be 
suitable for an albumin test. 



PHYSICAL PROPERTIES OF URINE 



329 



Specific Gravity. — The gravity is most conveniently taken 
with a urinometer (Fig. 27). Care should be taken in the 
selection of this instrument so that the scale graduation may be 
accurate. The fact that the instrument will sink in distilled 
water at the proper temperature (usually 6o° F., 15!° C.) to 
the zero mark, is not a sufficient proof of its accuracy, as many 
cheap instruments will do this, and give erroneous readings 
at the higher markings of the scale. Distilled water is rep- 
resented by 1000, and the relative increase in the comparative 
gravity of urines will be easily represented on the scale ranging 
from 1000 to 1050. As the first two figures of the specific 
gravity are always the same (10) they are usu- 
ally omitted from the scale which is made to 
read from o to 50 or 60. The reading should be 
made, if possible, from underneath the surface 
of the liquid, as the liquid is usually drawn 
around the stem by adhesion, so that accurate 
readings from the surface are difficult. The 
specific gravity of normal urine is from 1018 to 
1022; it decreases in cases where the quantity is 
much above the normal (polyurias) , unless sugar 
is present. It is increased by the presence of 
sugar or by concentration, whereby the normal 
solids are relatively increased. In case the quantity of urine 
is too small for the determination of the gravity in the usual way, 
the urinopyknometer, devised and recommended by Dr. Saxe in 
his " Examination of the Urine," may be employed. See page 
307, on specific gravity of saliva. 

Reaction. — The reaction of urine is normally acid to litmus- 
paper, due in part to the presence of acid sodium phosphate, 
and in part to organic acid combinations, the composition of 
which is unknown. The degree of acidity is roughly indicated 
by the intensity of color produced with the carefully prepared 
litmus-paper. More accurate results may be obtained by a 




Fig. 27. 



330 URINE 

regular volumetric examination (with N/20 alkali), or by the 
test for urinary acidities given by Freund and Topfer who 
suggest the following method : 

" To 10 c.c. of the urine add two to four drops of a 1% solu- 
tion of alizarin. If the resulting color is pure yellow, free acids 
are present; if deep violet, combined acid salts. If none of 
these colors appear, there are present acid salts of the type 
of disodic phosphate. The amount of one- tenth normal hydro- 
chloric acid standard solution required to produce a pure yel- 
low color represents the alkaline salts, while the amount of 
one-tenth normal sodium hydrate required to cause a deep 
violet represents the acid salts." 



CHAPTER XXXVIII. 
NORMAL" CONSTITUENTS OF URINE. 

The more important normal constituents of the urine are 
urea, uric acid (combined as urates), chlorides, phosphates, 
sulphates, indoxyl, coloring matters; traces of mucin, organic 
acids, carbonates, hippuric acid, creatin, and creatinin may also 
be present. The total normal solids are composed approxi- 
mately of 50% urea, 25% chloride of sodium; at least one-half 
of the remainder are phosphates and sulphates. We see that 
the constituent which most influences the specific gravity is the 
urea, and in normal samples the specific gravity is an index of 
the amount of urea present. The total solids may be calcu- 
lated by multiplying the last two figures of the specific gravity 
by 2 J,* which will give approximately the number of grams of 
solids in one liter of urine; from this the solids in the twenty- 
four-hour amount may be easily calculated. 

Urea. 
The chemistry of urea has been already considered (page 

237). 

Detection. — A qualitative test for this substance is obvi- 
ously superfluous, although such may be made by obtaining 
the crystals of urea nitrate or oxalate (page 238). The quan- 
tity of urea is of great importance, especially in cases where 
there is any question in regard to the body metabolism or the 
amount of nitrogen excreted. By far the greater proportion 
of all nitrogenous waste is eliminated by the kidneys in the 
form of urea, a comparatively slight amount as other nitroge- 

* Coefficient of Haeser. 
33i 



33* 



URINE 



nous constituents of the urine, a still smaller amount in the 
feces, and traces only by other avenues. The urea may be 
quantitatively determined by various methods, the hypobro- 
mite method being the most practical. See reaction on page 238. 

Quantitative Determination. — There are various forms of 
apparatus used in connection with this process. 

The one devised by Dr. Squibb is pictured in Fig. 28. It 
has been quite generally used; hence its description is given. 
It is not recommended, because a source of considerable error 




Fig. 28. 

lies in the fact that the gases (C0 2 and N) evolved from the 
urea are very apt to be driven over into bottle A before all the 
CO2 has been absorbed by the reagent in B and consequently 
the results are higher than they should be. 

The first step in the use of this apparatus is to completely 
nil the bottle A, including the tubes D and H, with water, 
with the glass plug E closing the lower end of D. Next put 
5 c.c. each of a 40% solution of caustic soda and a bromine 
solution in potassium bromide * into B. Place the stopper in 
B and connect the tube C at H, then fill accurately the 2-c.c. 
pipette with urine. Place in position in the stopper of B as 
shown in the cut, remove E from the rubber tube D, and allow 

* For preparation of this solution see Appendix. 






NORMAL CONSTITUENTS OF URINE 



333 



D to fall to the bottom of the graduate as indicated. Pressure 
is now applied to the bulb of the pipette, so that the 2 c.c. 
of urine is forced with moderate rapidity into the bottle. As 
the pressure on the bulb is released, water will be drawn back 
into A, and it is essential that the end of D be under water 
during this part of the process. Bottle B should be agitated 
to insure complete decomposition of the urea. Nitrogen and 
carbon dioxide are at once evolved according to the reaction on 
page 238. The 40% solution of caustic soda is strong enough 
to absorb and hold the C0 2 . The nitrogen passes A 

into A , forcing a corresponding volume of water 
into the graduate. This volume of gas, read in 
cubic centimeters of the water, will give the 
percentage of urea in the sample examined, 1 c.c. 
of nitrogen being equivalent to 0.126 gram of 
urea. 

The Doremus-Hinds apparatus shown in 
Fig. 29 gives a perfectly satisfactory method 
for the estimation of urea by the hypobromite 
method. The reagent, equal parts of bromine 
solution and 40% NaOH (x\ppendix, page 427), 
is introduced into R and the tube completely 
filled. The tube U is next filled exactly to the zero mark, 
then by means of the stop-cock 5 1 c.c. of urine is allowed 
to enter T a few drops at a time and slowly enough to pre- 
vent any escape of gas through R. The gas rises in small 
bubbles through a comparatively long tube and remains in con- 
tact with the reagent which insures perfect absorption of CO2, 
thus overcoming the greatest objection to the Squibb 's apparatus. 

The tube T is graduated to read centigrams of urea in 1 c.c, 
of urine. 

A more accurate determination of urea depends upon the 
conversion of urea into ammonia by various methods which 
make quantitative application of the Kjeldahl determination 




Fig. 29. 



334 URINE 

of nitrogen. These are given in excellent detail in Hawk's 
Fifth Edition of " Practical Physiological Chemistry " and to 
this work the student is referred. 

Uric Acid. 

Uric acid and its antecedents, the xanthin bases, are derived 
from the decomposition of nuclein and nucleoprotein. For 
chemistry of this substance, see pages 240 to 243. The uric 
acid is increased by a highly nitrogenous diet and certain vege- 
table substances which contain purin (page 241) derivatives, 
such as coffee, tea, and cocoa. The so-called red meats, beef, 
mutton, etc., are regarded as the most abundant source of uric 
acid and urates. As previously suggested uric acid does not 
occur in normal urine as such, but is combined with the alka- 
line bases. 

Determination. — It is unnecessary to make a qualitative test 
in urine, as urates are always present. If a qualitative test is 
desired the murexide test, as given on page 394, is available. 
Uric acid and allied constituents of the urine are conveniently 
determined quantitatively by the centrifugal method as de- 
vised by Dr. R. Harvey Cook.* The detail of this method is 
as follows: Measure 10 c.c. of urine into a graduated tube, 
used in the centrifugal machine, add a few grains of sodium 
carbonate, and about 3 c.c. of strong ammonium hydrate. 
Place in the centrifuge, and allow to run for one or two minutes, 
then carefully decant the clear urine into another graduate 
tube, leaving the precipitate which consists of earthy phos- 
phates. The bulk of this precipitate may be noticed and an 
idea obtained as to whether the earthy phosphates are present 
in normal quantities or not. To the clear urine add 2 or 3 c.c. 
of ammoniacal silver-nitrate solution (AgN03, 5 grams; dis- 
tilled water, 80 c.c; strong ammonia, 20 c.c), and run in the 
centrifuge till the precipitate of silver urate has reached its 

* Medical Record, Mar. 12, 1898, page 373. 



NORMAL CONSTITUENTS OF URINE 335 

lowest obtainable reading. The ammonia will prevent the pre- 
cipitation of chlorides and, unless iodides or bromides are present, 
the precipitate will be fairly pure silver urate, each tenth of a 
cubic centimeter of the precipitate being equivalent to 0.001176 
gram of uric acid in the 10 c.c. of urine used, or 0.61176%. 

The silver precipitate is by no means pure silver urate, many 
of the other nitrogenous bases in urine forming insoluble silver 
salts. These occur only in very slight traces; so, for clinical 
purposes, the method is available unless the sample contains 
bromides or iodides, when iodide or bromide of silver will be 
formed, insoluble in the amount of ammonia usually used. 
More accurate results may be obtained by either Hopkins' or 
Folin's method. These are somewhat similar and consist of 
precipitation of the uric acid as ammonium urate. 100 to 
200 c.c. of urine is used and the precipitation effected by a 
saturated solution of NH4CI (Hopkins' method) or ten grams 
ammonium sulphate (Folin's method). 

The precipitate is washed in the reagent and dissolved in 
boiling water and the amount of uric acid determined by titra- 
tion with N/20 permanganate of potassium. Each cubic centi- 
meter of KMn0 4 used is equal to 0.00375 gram of uric acid. 

Ammonia Determination. 

The amount of ammonia normally present in urine is about 
0.7 gram in the 24-hour amount. Ammonia is increased in any 
systemic condition resulting in an increase of acidic elements 
(Acidosis), or upon ingestion of ammonium salts of inorganic 
acids, i.e., salts not easily oxidized to urea. 

Normally, the quantity of NH 3 follows more or less closely 
the urea and the protein metabolism, and amounts to about 
one-twentieth of one per cent. (0.05%) or about 0.7 gram in 
twenty-four hours. 

Determination may be made as follows: 

Folin's New Method. — Measure, by use of standardized 



336 URINE 

" Ostwald pipette," i or 2 ex. of urine into a large Jena test- 
tube. Then proceed exactly according to method given for 
saliva on page 310. 

Formaldehyde Method. — Place 10 c.c. urine in a 250 c.c. 
Erlenmeyer flask, add 50 or 60 c.c. H 2 0, titrate with N/10 NaOH 
with phenolphthalein as an indicator. The amount of NaOH 
used will represent total acidity of sample. 

After exact neutralization add 10 c.c. of previously neutral- 
ized commercial formaldehyde solution and titrate again with 
N/10 NaOH. The second amount of alkali added represents 
ammonia as follows: 
4 NH4CI + 6 CH 2 + 4 NaOH = N 4 (CH 2 ) 6 + 10 H 2 + 4 NaCL 

As the ammonium salts and the caustic soda react molecule 
for molecule it is possible to make calculation for quantity of 
NH 3 by multiplying the N/10 factor (0.0017) by the number of 
cubic centimeters of N/10 NaOH used. 

In cases of diabetes when the ammonia reaches a compara- 
tively large amount the figures obtained by this process will be 
found to be a little high, as amino acids are also acted upon by 
the NaOH, and will be calculated as ammonia, but for ordinary 
work of clinical comparisons this method is very simple and 
sufficiently accurate. 

This method is not affected by urea, uric acid, creatin, crea- 
tinin, purin bases, or hippuric acid.* 

Chlorides. 

The chlorides are represented in the urine chiefly by sodium 
chloride. This is present to the extent of from twelve to twenty 
grams in twenty-four hours. An increase above this quantity 

* Dr. Hans Malfatti in Zeit. fur Anal. Chemie, 47, page 273. 

Note. — See also the Vacuum Distillation Method, giving very exact results 
when properly carried out: 

H. Bjorn Andersen und Marius Lauritzen, Zeit. fur Physiol. Chemie, 64, 
page 21. 



NORMAL CONSTITUENTS OF URINE 337 

is unusual, although it simply indicates an increase in the in- 
gested salt, and is without clinical significance. The chlorine 
is diminished in dropsy, acute stages of pneumonia, and in 
fevers generally. 

Detection. — The usual qualitative test with silver nitrate 
and nitric acid is employed for detection of chlorine in the urine. 
If one drop of a strong solution of silver nitrate (1 to 8) is al- 
lowed to fall into the wine-glass in which the albumin test 
has been made (q.v.), the appearance of the resulting precipi- 
tate will give a rough idea of the quantity of chlorine present. 
If a solid ball of silver chloride is formed which does not become 
diffused upon gently agitating the contents of the glass, the 
chlorine is normal or increased. If the precipitate falls as a 
cloud distributed throughout the liquid, the chlorine is dimin- 
ished. The chlorine may be determined by precipitation with 
silver nitrate in 10 c.c. of urine, and the precipitate settled in a 
centrifuge-tube to constant reading, but this method is not 
recommended, as the precipitate is a bulky one, and usually 
takes a long time for thorough settling. The titration with 
silver nitrate, using potassium chromate as an indicator, really 
takes less time, and is much more accurate. This titration is 
made in the usual way (see page 159), except that, inasmuch as 
phosphates and urates are also precipitated, from three-tenths 
to 1 c.c. may be deducted from the amount of the silver-nitrate 
solution used according as it is much or little, thus allowing 
for these substances. An accurate titration of chlorine is 
described on page 161. But, as a rule, the simpler method 
gives results which for clinical purposes are equally valuable 
with those of this more tedious though more accurate process. 

Phosphates. 
The phosphates in the urine are of two kinds, the alkaline 
phosphates, Na 2 HP0 4 and NaH 2 P0 4 , etc., and the earthy phos- 
phates represented by the magnesium and the calcium phos- 



338 URINE 

phates. The phosphates are normally present to the extent 
of two and a half to three and a half grams, calculated as P 2 5 
(in twenty-four hours). 

The triple phosphates, ammonium magnesium phosphates 
(Plate IV, Fig. 2, page 172), are the forms in which phosphoric 
acid is usually found in urinary sediment. Crystals of acid 
calcium phosphate are occasionally found, and resemble the 
acid sodium urate in form (Plate X, Fig. 3, page 355), except that 
they are usually a little broader and more often occur in fan- 
shaped clusters. They may be distinguished by treatment with 
acetic acid, which dissolves the calcium phosphate promptly, 
while the urate is slowly dissolved and crystals of uric acid 
appear after a little time. The phosphates are deposited from 
neutral or alkaline urines and when this precipitation takes 
place within the body, the crystals cause more or less irritation 
to the urinary tract and may form aggregations which result 
in calculi. Phosphates are supplied by either a cereal or meat 
diet. They may be much increased in diseases accompanied 
by nervous waste, or by softening and absorption of bone. 
Phosphates are diminished in gout, in chronic diseases of the 
kidney, and during pregnancy. 

Detection. — A qualitative test for earthy phosphates (E.P.) 
may be made by taking a test-tube half full of urine, and 
making alkaline with ammonium hydrate. When the precipi- 
tate has thoroughly settled, if it is about 1/4 to 1/2 inch in 
depth, it represents normal, earthy phosphates. If this mix- 
ture is now filtered, the alkaline phosphates (A. P.) may be 
determined in the filtrate by the addition to the solution of 
one-third its volume of magnesium mixture.* The precipitate 
after settling will be 1/2 to 3/4 of an inch in depth if normal. 
The total phosphates may be determined in the centrifugal 
machine by adding 5 c.c. of magnesium mixture to 10 c.c. of 
urine. Each tenth of a cubic centimeter of the centrifugalized 

* See Appendix. 



NORMAL CONSTITUENTS OF URINE 339 

sediment will be equivalent to 0.00225 gram of P 2 5 in the 10 c.c. 
used. 

A more accurate determination of the total phosphoric acid 
may be made by the titration with uranium nitrate or acetate 
solution as follows: 

Reagents Required. — First, A standard uranium solution 
may be prepared as follows: Dissolve 35.5 grams of pure ura- 
nium nitrate or acetate in about 800 c.c. of distilled water; 
add three or four c.c. of glacial acetic acid and heat it enough 
to complete solution. Allow to stand over night, filter care- 
fully, and make up to 1000 c.c. Standardize this solution 
against crystallized microcosmic salt by dissolving 14.721 grams 
of the pure salt (NaNH HP0 4 . 4 H 2 0) in sufficient water to 
make 1000 c.c. Then titrate 20 c.c. of this solution, to which 
has been added 30 c.c. of water and 5 c.c. of sodium acetate 
solution, with the uranium solution (method of titration is 
given under process below) . 

The uranium solution should then be adjusted (diluted) so 
that it will take exactly 20 c.c. for this titration, when one c.c. 
of the uranium will be equivalent to five milligrams of P2O5. 

Second. A sodium acetate solution containing 100 c.c. of 
30% acetic acid and 100 grams of sodium acetate in enough 
distilled water to make 1000 c.c. 

Third. An indicator consisting of a saturated solution of 
potassium ferrocyanide. 

Process. — Place 50 c.c. of urine with 5 c.c. of sodium acetate 
solution above described in a small Erlenmeyer flask and heat 
nearly to the boiling-point. Titrate, while hot (8o° or above), 
with the standard uranium solution till a drop of the mixture 
placed on a white porcelain tile with a drop of the indicator 
(K4FeCy 6 ) gives a distinct brown color. This method of de- 
termining the end point is known as " spotting " and with a 
little practice gives very accurate results. 

The number of cubic centimeters of uranium solution multi- 



34° URINE 

plied by o.oi will give the weight of P 2 5 in ioo c.c. of urine 
(i c.c. of reagent being equal to 0.005 gram P2O5). 

This same process may be used for saliva by diluting the 
reagent one part to five, and preparing the sample for titration 
as follows: Take from 2 to 5 c.c. saliva, add sufficient alcohol 
to make 10 c.c. of mixture, warm, and filter. This serves to 
separate the protein substance. Take 5 c.c. of the filtered 
solution and titrate with the diluted uranium solution as by 
the process given above for urine. In this case, of course, 1 c.c. 
of the standard uranium will represent one milligram of P2O5 
rather than five. 

Sulphates. 

The sulphates in the urine are present as alkaline sulphates, 
K2SO4 and Na:S0 4 ; also as ethereal sulphates, represented by 
such compounds as indoxyl potassium sulphate, page 253. 

Detection and Determination. —The sulphates may be de- 
tected by precipitation with barium chloride in hydrochloric 
acid solution. If the precipitate is obtained from 10 c.c. of 
urine and centrifugalized to constant reading, the per cent, of 
sulphuric acid by weight will be one-fourth of the volume per 
cent, of the precipitate. The sulphates follow rather closely 
the urea, and their determination is not of great importance. 
They are increased in acute fevers, diminished in chronic diseases 
generally, and markedly diminished in carbolic-acid poisoning. 
(Ogden.) 

Determination of Total Sulphur. — (J. Benedict, Biol. Chem., 
6, 363; W. Denis, J. Biol. Chem., 8, 401.) To 25 c.c. of urine 
contained in a porcelain evaporating dish (10-12 cm. diameter) 
add exactly 5 c.c. of a solution containing 25 per cent, copper 
nitrate, 25 per cent, sodium chloride, and 10 per cent, ammonium 
nitrate. Evaporate to dryness over a water-bath. Then heat 
over a name, gradually increasing the heat until the dish is 
red hot, and continue heating for 10 to 15 minutes. Allow to 



NORMAL CONSTITUENTS OF URINE 341 

cool. Add 20 c.c. dilute hydrochloric acid and warm gently. 
Rinse into a flask or beaker by means of about 100 c.c. hot 
water. Heat to boiling, and add drop by drop 25 c.c. of a 
10 per cent, barium chloride solution. Filter, wash, ignite, and 
weigh. 

Coloring Matter. — Urobilin, an important coloring matter 
of the urine, exists as a parent substance or chromogen to which 
has been given the name urobilinogen. This undergoes de- 
composition by action of light with liberation of urobilin. 

Urobilin is without doubt derived from the bilerubin of the 
bile, which, in turn, comes from the hemochromogen of the 
blood. Dr. J. B. Ogden is authority for the statement that "it is 
safe to infer that the amount of urobilin in the urine is a meas- 
ure of the destruction of the hemoglobin or blood pigment. " 

Urochrome is a pigment to which the yellow color of urine 
is chiefly due. Uroerythrin "and urorosein are less important, 
existing only in very slight quantities, but they are responsible 
for colors of some sediments and of decomposition products 
which are noticed in analysis. 

Soluble Salts. 

An examination of the soluble salts of the urine is easily and 
often profitably made by simply allowing a large drop to evapo- 
rate spontaneously and examining the residue with the micro- 
polariscope. The alkaline chlorides are often seen but they 
do not polarize light. Crystalline phosphates, sulphates, urates, 
and oxalates do polarize light and may frequently be detected 
by their characteristic forms. The value of determination of 
soluble oxalates in this way is suggested on page 356. 

Indoxyl. 

The indoxyl is of considerable importance, as an increase 
above the normal amount is indicative of increased putrefac- 
tion of nitrogenous substances (tryptophan) taking place in the 



342 URINE 

small intestine. Indoxyl may also be increased by acute in- 
flammatory process of the peritoneal cavity. Ordinary con- 
stipation does not increase the indoxyl. The test for indoxyl 
depends upon the oxidation of the indoxyl potassium sulphate 
to indigo blue according to the following reaction : 

2 C 8 H 6 NKS0 4 + 2 = 2 C 8 H 5 NO + 2 KHS0 4 . 

Indoxyl potassium sulphate. Indigo. 

Note. — As tryptophan is a necessary constituent of any nitrogenous sub- 
stance from which indoxyl is produced, it may happen that a few protein sub- 
stances, such as gelatin which does not contain tryptophan, might be used in 
undue proportion and an excessive putrefaction would not be accompanied by 
indoxyl, but the nitrogenous food substances generally contain sufficient tryp- 
tophan to make the first statement of this paragraph practically true. 

Detection and Determination. — 15 c.c. of strong HC1 is 
placed in a wine-glass, and a single drop of concentrated nitric 
acid added; then thirty drops of urine are stirred into the 
mixture. If indoxyl is present, an amethyst color develops in 
from five to fifteen minutes. If the color is purple, the indoxyl 
is increased. Variation of the amount of indoxyl within normal 
limits is rather wide, and the indoxyl may be reported as high 
or low normal, increased, or diminished. 



CHAPTER XXXIX. 
ABNORMAL CONSTITUENTS OF URINE. 

The principal abnormal constituents are albumin, sugar, 
acetone, bile, and various crystalline salts, discoverable either 
by microscopical examination of the sediment, or by evapora- 
tion of a clear fluid, and examination with the micropolariscope. 

Metallic substances, arsenic, lead, and mercury are occa- 
sionally present, and tests should be made for them when gen- 
eral symptoms or the conditions of the kidney indicate metallic 
poison. Albumin is probably present in minute traces in the 
majority of urines. When in sufficient quantity to be detected 
by the usual laboratory methods, it is essential that we learn 
the source from which it has been derived, for the simple pres- 
ence of even a considerable trace of albumin may be of but 
slight clinical importance. Albumin may indicate either a 
pathological condition of the kidney, which allows the entrance 
into the renal tubules of serum-albumin from the blood, or it 
may indicate a change in the composition of the blood, whereby 
the albumin passes more easily through the renal membranes, 
or its presence may be due to irritations from various sources 
of the urinary tract; and, as regards the bearing of albuminurias 
on dental disease, it is sufficient simply to determine whether 
renal disturbance is primary or secondary to some other trouble, 
such as heart disease; or purely local, as when caused by irri- 
tation due to crystalline elements. 

Detection. — Albumin may be detected by either of two 
simple methods. It is often desirable to use both of these 
methods, thereby eliminating possible confusion from the 

343 



344 URINE 

presence of substances other than albumin, which may respond 
to one of the two tests, but not to both. 

The first consists simply in underlaying about 25 c.c. of 
filtered urine in a wine-glass with concentrated nitric acid. 
The wine-glass should be tipped as far as possible and the acid 
allowed to run very slowly down the side. This method is 
preferable to the use of the apparatus known as the albumino- 
scope or Horismascope (Fig. 30). As this latter method does 




Fig. 30. Fig. 31. 

not provide for sufficient mixing of nitric acid with the sample, 
the albumin is shown by a narrow white ring at the plane of 
contact of the two liquids. A white ring above the plane of 
contact is not albumin, but is composed of acid urates, indi- 
cating an excess of urates in the sample (Fig. 31). The albumin, 
in distinction from this band, occurs directly above the acid and 
is usually reported as the slightest possible trace when just 
discernible; as a slight trace, when well marked, but not dense 
enough to be seen by looking through the liquid from above; 
as a trace, when the white cloud may be seen by looking down 
into the glass from above and a large trace if plainly visible in 
this way. 

Acetic acid and heat method of testing for albumin is the 
other method referred to in the preceding paragraph. It is of 
about the same delicacy as the nitric acid test, and is less liable 
to respond to substances other than albumin. It is made as 
follows: 



ABNORMAL CONSTITUENTS OF URINE 



345 




A test-tube is filled two-thirds full of perfectly clear filtered 
urine, one drop of acetic acid added and the upper half of the 
sample boiled. The tube can easily be held in the hand by the 
lower end. After boiling, if the tube is examined before a black 
background, a slight cloudiness or turbidity resulting from 
coagulated albumin can be easily detected in the upper part of 
tube. Anything more than a trace should be determined in 
the centrifugal machine by mixing 10 c.c. of filtered urine 
with about 2 c.c. of acetic acid and 3 c.c. of potassium 
ferrocyanide solution. Each tenth of a cubic centimeter 
of the precipitated albumin, when settled to constant 
reading, indicates one-sixtieth of one per cent, albumin 
by weight. This factor is fairly correct up to four- or 
five- tenths of a cubic centimeter of precipitate; beyond 
this it is of little value, and the albumin is best deter- 
mined quantitatively by measuring 50 or 100 c.c. of 
urine into a small beaker, adding a drop of acetic acid, 
and boiling, which will completely precipitate the al- 
bumin. It may then be filtered into a counterpoised 
filter, thoroughly washed, first in water, next in alcohol, 
and lastly in ether, dried at a temperature a little 
below the boiling-point of water, and weighed. Esbach's 
method may be of value in some instances, and is carried out 
as follows: 

Fill the albuminometer (Fig. 32) with urine to the line U, 
and then add the reagent* to the line R; close the tube, mix 
the contents thoroughly, and allow to stand in an upright 
position for twenty-four hours. At the end of that time the 
depth of precipitate may be read by the figures on the lower 
part of the tube, these figures representing tenths of one per 
cent, of albumin, or grams of albumin in a liter of urine. If a 
sample of urine contains more albumin than is easily estimated 

* Esbach's reagent consists of picric acid, 10 grams; citric acid, 20 grams, and 
distilled water sufficient to make one liter. 



Fig. 32. 



346 URINE 

by the centrifugal or Esbach's method, approximate results will 
be obtained by diluting with several volumes of distilled water, 
until the quantity of albumin precipitated is within the limit 
of the test. The proteoses occasionally occur in the urine, and 
are distinguished from albumin by the fact that they redissolve 
at a boiling temperature. If filtered while hot, albumin, which 
usually accompanies them, will remain on the paper, while 
albumose will separate from the clear filtrate as it cools. 

Sugar. 

Sugar in urine represents a perverted process of oxidation 
for which the pancreas is largely responsible. The liver also 
often plays an important part in cases of diabetes, but just 
how this is done is not clearly known. Sugar in the urine 
does not of necessity indicate diabetes any more than albumin 
indicates Bright's disease. Many cases of glycosuria are of a 
temporary nature and respond readily to dietary treatment. 
Whenever sugar is found it is desirable to make tests upon both 
a fasting and an after-meal sample, such as might be obtained 
before breakfast and one hour after dinner. If the fasting 
sample is comparatively free from sugar, it indicates that the 
glycosuria is of a temporary nature and due to faulty metabo- 
lism, rather than to any organic disease of the liver or pancreas. 

Detection. — Sugar in the urine may be detected by several 
general carbohydrate tests, as previously given. 

Fehling's test. This test is very generally employed (Exp. 
167, page 401). It is best, however, to modify it by bringing 
the Fehling's solution to active ebullition, adding from five to 
thirty drops of the suspected sample and allowing to stand 
without further heating. This prevents possible reduction of 
the sugar by xanthin bases or other occasional constituents of 
the urine, which might give misleading results if the mixture 
were boiled after addition of the sample. There is less danger 
of trouble of this sort if the gravity of the urine is below normal. 



ABNORMAL CONSTITUENTS OF URINE 347 

If it is necessary to make a rapid test, the mixture may be 
boiled after the urine is added, and in case the result is negative 
there is no need of further test; if, however, a slight reduction 
of the copper solution takes place, it will be necessary to repeat 
the test, using the precaution above given. Quantitatively, 
sugar may be determined by the use of Fehling's solution as 
follows : 

If the urine contains more than a trace of albumin, this 
substance should be removed by adding a drop of acetic acid 
and heating; after filtration the sample should be cooled and 
restored to original volume with distilled water. If specific 
gravity of the urine is more than 1025, it should be diluted to 
ten times its volume with distilled water (urine, one part; water, 
nine). If the gravity is less than 1025, dilute it to five times its 
volume, mix, and fill a 25 c.c. burette. In a 250 c.c. flask place 
10 c.c. each of the alkaline tartrate and copper sulphate solu- 
tions (Fehling's solution), and add about 100 c.c. of distilled 
water. Place the flask over a Bunsen burner, and bring to a 
boil. If no change takes place after a minute or two of boiling, 
add the solution from the burette gradually, until the precipi- 
tate becomes sufficiently dense to obscure the blue color of the 
solution. Continue to boil for one or two minutes, then re- 
move from the flame and watch carefully the line directly 
beneath the surface of the liquid, which will appear blue until 
all of the copper has been reduced to the red suboxide. The 
solution should be kept at the boiling-point throughout the 
entire operation, except, in making the examination of the 
meniscus between the additions of the diluted urine. These 
additions must be made very carefully, and as the process nears 
completion not more than one or two drops should be added 
at a time. When the blue color has entirely disappeared, and 
the fine of meniscus has become colorless, note the number of 
cubic centimeters of dilute urine used, and calculate that in 
that quantity there is an equivalent of 0.05 gram of glucose; 



34S URINE 

in other words, 0.05 gram of glucose will exactly reduce the 
amount of Fehling's solution used, and from this fact the amount 
of glucose in the entire twenty-four hour amount of urine is 
easily calculated. If the titration is carried beyond the proper 
" end point " the meniscus will appear yellow instead of 
colorless. 

Benedict's test. The following application of Benedict's so- 
lution to the detection of sugar in urine is taken from a paper 
by Stanley R. Benedict in the Journal of the American Medical 
Association, October 7, 191 1. "For the detection of glucose 
in urine about 5 c.c. of the reagent are placed in a test-tube 
and eight to ten drops {not more) of the urine to be examined 
are added. The mixture is then heated to vigorous boiling, 
kept at this temperature for one or two minutes, and allowed 
to cool spontaneously. In the presence of glucose the entire 
body of the solution will be filled with a precipitate, which may be 
red, yellow or greenish in tinge. If the quantity of glucose be 
low (under 0.3 per cent) the precipitate forms only on cooling. 
If no sugar be present the solution either remains perfectly 
clear, or shows a faint turbidity that is blue in color, and con- 
sists of precipitated urates. The chief points to be remembered 
in the use of the reagent are (1) the addition of a small quantity 
of urine (8 to 10 drops) to 5 c.c. of the reagent, this being de- 
sirable not because larger amounts of normal urine would cause 
reduction of the reagent, but because more delicate results are 
obtained by this procedure, (2) vigorous boiling of the solution 
after addition of the urine, and then allowing the mixture to 
cool spontaneously, and (3) if sugar be present, the solution 
(either before or after cooling) will be filled from top to bottom 
with a precipitate, so that the mixture becomes opaque. Since 
bulk, and not color, of the precipitate is made the basis of a 
positive reaction, the test may be carried out as readily in 
artificial light as in daylight, even when examining for very 
small quantities of sugar." 



ABNORMAL CONSTITUENTS OF URINE 349 

The fermentation test (Exp. 172, page 401) may also be used 
to detect the presence of sugar and, approximately, the amount. 

The fermentation test for sugar is a convenient and easily 
made qualitative test, it being only necessary to fill a fermen- 
tation tube (Fig. 38, page 401) absolutely full of urine to which 
a small portion of yeast has been added, and to allow the tube 
to stand in a warm place for several hours. Any collection of 
gas in the top of the tube will indicate the presence of sugar. 
This method may also be used as a quantitative test for sugar 
by taking two portions of the same sample, adding yeast to 
one, and using the other as a control. At the end of twenty- 
four hours, CO2 is removed from fermented sample, the specific 
gravity of both samples is carefully taken, and the loss of 
density in the fermented sample is calculated as sugar by multi- 
plying the number of degrees lost in gravity by 0.23, water 
being considered as 1000. 

The phenyl-hydrazine test may be used as a confirmatory test 
or in cases where very minute quantities are suspected. This 
test is considered about ten times as delicate as the Fehling's 
test; consequently, it may show small amounts of sugar which 
are not detected by the more rapid process. 

The optical analysis for sugar may be made with a polariscope, 
preferably constructed for use on urine. This determination 
depends upon the ability of glucose to rotate the plane of polar- 
ized light towards the right, the degree of rotation indicating 
the amount of sugar in a pure solution. Of course, allowance 
or correction must always be made for the presence of any sub- 
stances which will rotate the light in the opposite direction, 
such as albumin, levulose and /3-oxybutyric acid. 

For the detail of construction and use of the polariscope, 
the student is referred to the more complete works on urine 
analysis by Ogden, Holland, or Purdy. 



350 URINE 

Acetone. 

Acetone may occur in the urine as a result of various patho- 
logical conditions and according to von Noorden they are all 
due to some one-sided perversion of nutrition. The acetonurias 
attendant on diabetes, scarlet fever, pneumonia, small-pox, etc., 
are of less practical interest to the dental practitioner than 
those more often overlooked by the medical profession, and 
which indicate improper diet, possibly resulting in serious 
malnutrition. The following points may be noted: In ad- 
vanced stages of diabetes, acetone appears in the urine accom- 
panied by diacetic acid. An increased ingestion of proteins 
may result in the appearance of acetone, in which case the 
direct cause is more an " insufficient utilization of carbohy- 
drates " * than the increase of protein. Acetone may result 
from the oxidation of /3-oxybutyric acid. Diacetic acid is first 
formed, and subsequently the carboxyl group is replaced by 
an atom of hydrogen, as shown by the following graphic formulae: 

0-oxybutyric acid : CH 3 - CHOH - CH 2 - COOH. 
Diacetic acid : CH 3 - CO - CH 2 - COOH. 
Acetone: CH3-CO-CH3. 

Detection. Acetone may be detected in the urine by the 
production of iodoform, as described under analysis of saliva 
on page 313, but it is not in this case nearly so delicate a test 
on account of the odor and acid character of the urine. A 
more useful test is known as Legal's test and is made as follows: 
To a third of a test-tubeful of urine add a few drops of a freshly 
prepared and fairly concentrated solution of sodium nitro- 
prusside, next add two or three drops of strong acetic acid, and 
then a considerable excess of ammonia. If the contents of the 
tube are mixed by a rather rapid rotary motion without invert- 
ing or violent shaking, the ammonia will not reach the bottom 

* von Noorden's Diseases of Metabolism and Nutrition. 



ABNORMAL CONSTITUENTS OF URINE 351 

of the tube, and the presence of acetone will be indicated by a 
violet-red band above the layer of acid liquid. If much acetone 
is present a deep violet to purple color is obtained. 

Diacetic Acid occasionally occurs in urine as an abnormal 
constituent most commonly in advanced stages of diabetes, 
usually accompanied by acetone and /3-oxybutyric acid. It 
may be detected by adding to the urine a little ferric chloride, 
when a dark wine-red color is produced. If a precipitate of 
ferric phosphate is obtained, filter the urine and examine the 
filtrate for color. This test may be made fairly distinctive for 
diacetic acid by boiling and cooling a second portion of the 
urine previous to making the test, when the result will be nega- 
tive if the color at first produced was due to diacetic acid. 

/3-oxybutyric Acid. — This substance usually accompanies 
diacetic acid as above stated. Determinations of the quantity 
present cannot be made by any simple method. Perhaps the 
most practical method is by Bloor's nephelometer, page 296. 

Bile. 
Bile may occur in the urine as such, due to pathologic con- 
ditions of the liver- or bile-ducts, as stated on page 322. The 
coloring matters of the bile may also occur from causes aside 
from lesions of the liver. A urine containing bile or bile-pig- 
ments is always more or less highly colored, and upon shaking 
the foam will be of a yellow or greenish-yellow color. Albumin 
and high indoxyl accompany the presence of bile and there is 
also usually considerable renal disturbance. It may be de- 
tected by carefully adding to one-half a wine-glass of the sus- 
pected sample a few cubic centimeters of the alcoholic solution 
of iodine (tincture of iodine). A green color will be observed 
just beneath the line of contact of the two liquids (page 423). 
The test may be conveniently made by placing the iodine first 
in the wine-glass and then with a pipette introducing the urine 
beneath the iodine solution. 



352 v URINE 

Metallic Substances. 

Arsenic, mercury, and lead are the three metals which it 
may be necessary to look for in a sample of urine. The method 
for the detection of mercury, given on page 317, is applicable 
for this purpose. 

Arsenic may be detected by the Marsh-Berzelius test (page 
36), after oxidizing all organic matter. The process may be 
carried out as follows: Evaporate to dryness a liter of urine, 
to which 200 c.c. of strong nitric acid has been added; add to 
the residue, while still hot, from 15 to 20 c.c. of concentrated 
sulphuric acid. This must be done in a large porcelain evapo- 
rating-dish, or else the acid must be added very slowly to prevent 
frothing over and loss of a portion of the sample. After the 
action has quieted down the whole mixture may be trans- 
ferred to a 500 c.c. Kjeldahl flask and heat applied, gradually 
at first, and then more strongly. It will be necessary to add 
from time to time small portions of nitric acid and possibly a 
little more sulphuric acid; as the oxidation progresses the 
liquid in the flask becomes lighter in color and at the comple- 
tion of the process is water-white, even when the temperature 
is increased so that sulphuric-acid fumes are given off. After 
cooling, the strongly acid liquid is diluted with four or five times 
its volume of water, filtered, if necessary, to remove excessive 
amounts of earthy sulphates, and is then ready for the arsenic 
test. 

Lead. — The sample of urine to be tested for lead should 
measure at least 1000 c.c, and should be tested for iodine to 
insure the fact that the patient has been under treatment with 
potassium iodide to dissolve lead salts, otherwise a negative 
result may be obtained when lead is actually present and poison- 
ing the system. Oxidize the sample in precisely the same 
manner as when making the arsenic test, up to the point of 
diluting the strong acid solution with water; then, in this case, 



PLATE IX —URINE. 




Fig. i. 
Ammonium Acid Urate. 




Fig. 3. — Pus. 
A , After addition of Acetic Acid. 





Fig. 2. 
Spermatozoa. 




Fig. 4. 
Renal Casts. 




Fig. 5. 
False Casts and Mucin. 



Fig. 6. 
A, Lycopodium; B, Moth-scales; C, Cork; 
D, Cotton-fibres; E, Wool-fibres. 



ABNORMAL CONSTITUENTS OF URINE 353 

use rather less water for the dilution, allow to cool, and neu- 
tralize with Squibb's ammonia, acidify quite strongly with 
acetic acid, and pass H 2 S gas into the solution. It is desirable 
to leave the solution saturated with H 2 S for at least twelve 
hours. Then filter, and without washing dissolve the precipi- 
tate in warm dilute nitric acid, evaporate the HN0 3 solution 
to dryness, add 5 c.c. of water, make alkaline with a drop or 
two of ammonia, and again acidify with acetic acid and add a 
solution of bichromate of potash.* Allow to stand several 
hours, filter off the chromate of lead, wash several times with 
distilled water, and lastly with H 2 S water when the lead chro- 
mate will blacken from the formation of lead sulphide. This 
stain is a superficial one and disappears upon standing, but 
when the process is conducted in this way it constitutes a very 
delicate and satisfactory test for lead in either urine or saliva. 

Urinary Sediments. 

The sediment which settles from a sample of urine upon 
standing consists normally of a slight amount of mucin and 
epithelial cells. It may contain also bacteria and a consider- 
able variety of extraneous matter, including starch grains, 
various vegetables spores, yeast cells, fibers from various fabrics, 
cotton, wool, flax from linen, etc., diatoms, scales from insects' 
wings, and other particles which may occur as dust (see Plate 
IX, Fig. 6; also Plate X, Fig. 4). Under abnormal conditions 
the sediment may contain crystalline elements, including uric 
acid and urates, phosphates, oxalates, cystin, tyrosin, leucin, 
etc., also organized elements such as epithelium, renal or other 
casts (Plate IX, Fig. 4), blood globules, pus cells (Plate IX, Fig. 
3), spermatozoa (Plate IX, Fig. 2), fat, mucin (Plate IX, Fig. 
5), etc. Urinary sediment may be thrown down from a fresh 
specimen by the use of a centrifuge, or the urine may be 

* Natural chromate of potash will precipitate copper, the acid chromate pre- 
cipitates lead only of the second group metals. 




354 URINE 

allowed to stand in a glass tube with rounded bottom for sev- 
eral hours, when the sediment settles to the bottom by gravity. 
If possible it is best to examine sediments settled in both of 
these ways, as the centrifuge will show elements, such as small 
casts, that would settle slowly, possibly not at all, by the gravity 
method. On the other hand, the sediment allowed to settle 
spontaneously will often give a more correct idea of compara- 
tive numbers of the various elements observed, than when 
settled in a centrifuge-tube. A drop or two of formalin may 
be used to preserve urinary sediment, as suggested on page 327, 
but if too much of this substance is used, especially in urines 
containing high percentages of urea, a compound is liable to 
be formed which has been called formaldehydurea (Plate X, 
Fig. 5), which settles with the sediment and seriously interferes 
with the microscopical examination. This compound may form 
sheaf-like crystals similar to tyrosin and may be mistaken for 
crystals of sodium oxalate, especially when examined with a 
low power objective. 

Uric Acid. — Uric acid is deposited from normal urine, upon 
standing, with an excess of free acid (HC1). Urines that have 
a high degree of acidity will also produce a like deposit, and the 
finding of uric-acid crystals does not necessarily signify that 
the crystallization took place within the body, unless special 
care has been taken that the sample examined was perfectly 
fresh, although the tendency to deposit uric acid is, of course, 
indicated. The urine from which uric acid separates, as such, 
is usually rather concentrated and of strong acid reaction. 
These crystals vary in appearance (Plate X, Figs. 1 and 2), 
but are almost always colored yellow to red. Colorless crystals 
are sometimes observed. They are usually quite small, but of 
the peculiar whetstone shape in which this acid most usually 
crystallizes. The presence of uric acid has practically no effect 
upon the acidity of the sample; for, if the acid separates in a 
crystalline form, it is insoluble, and if it does not separate it is 



PLATE X.— URINE. 




Fig. i. 
Uric Acid. 




Fig. 3. 
A, Sodium Urate; B, Sodium Acid Urate. 





Fig. 2. 
Uric Acid. 




Fig. 4. 
Yeast Cells and Molds. 



Fig. 5. 
Formaldehyd Urea (P. L.). 




ABNORMAL CONSTITUENTS OF URINE 355 

in combination as urates, possibly, of course, as acid urates. 
Uric acid exists normally in proportion to urea as about 1 to 50, 
but there is no necessary relationship between the quantities 
of the two substances, and the one may be diminished while 
the other is increased. 

Urates. — Urates may occur as crystalline or amorphous pre- 
cipitates. The crystalline urates are urate of sodium rarely, 
acid urate of sodium (Plate X, Fig. 3), and acid am- 
monium urate (Plate IX, Fig. 1, page 353). The amorphous 
urates are of the alkaline bases, usually sodium, and are fre- 
quently precipitated by lowering of the temperature after the 
sample has been passed, in such cases the urine assumes a cloudy 
appearance which is cleared up by the application of heat. A 
sediment consisting of urates is usually of a pinkish color. 

Phosphates. — Phosphates in the urinary sediment may be 
amorphous or crystalline. They are of the alkaline earths 
rather than of the alkaline metals, as the latter are soluble in 
both the acid and neutral forms. The amorphous phosphates 
deposit with the change of reaction from acid to alkaline, and 
usually in the form of a so-called triple phosphate of ammonia 
and magnesia (Plate IV, Fig. 2, page 172). This salt crystallizes 
in two forms. The prismatic form is the ultimate form; that 
is, if the crystallization takes place very slowly, the prismatic 
form is the one in which the salt is thrown out. If it takes 
place rapidly it may be precipitated in the feathery form, but 
this slowly changes over to the prismatic form. The acid 
phosphates may be precipitated closely resembling in appear- 
ance the acid urates (Plate X, Fig. 3), but may be distinguished 
from them by their ready solubility in acetic acid and failure 
to produce, after solution in acetic acid, any crystals of uric 
acid such as are obtained from the urates. 

Acid Lactates. — These are soluble salts, and are found in 
urine only by evaporation of a drop of the clear fluid and an 
examination of the residue by polarized light. When found 



356 URIXK 

in the urine, the significance is quite different from that when 
found in the saliva, as in the urine they may possibly be formed 
from lactates, which indicate a faulty action of the liver, and 
of course they have no connection with tooth erosion. The 
lactates furnish evidence of similar character. 

Oxalates. — Oxalates if found in the sediment usually occur 
as calcium oxalates. These crystals assume a variety of forms, 
as shown in Plate II, Fig. i, page 170. Sodium oxalate (Plate II, 
Fig. 4) may occur in the urine (not, however, in the sediment), 
and is detected only by evaporating a drop of the clear liquid 
and examining with polarized light. Dr. Kirk claims that an 
oxaluria may be detected in this way for a considerable time 
before the appearance of the oxalate of lime crystals, and hence 
such examination becomes a valuable aid to diagnosis. 

Cystin. — Cystin occurs as six-sided plates. It is a com- 
paratively rare crystal, and indicates insufficient oxidation, 
particularly of the organic sulphur compounds. 

Epithelium. — Epithelium occurs in the urinary sediment 
from any part of the urinary tract. In the male urine it is 
much easier to determine the character of the epithelium than 
in the female, as in the latter the comparatively large amount 
of mucous surface, from which epithelium may be gathered, 
furnishes a great variety of forms which are, of course, without 
clinical significance. The epithelium from the vagina may be 
quite readily distinguished as very large cells with small nuclei, 
lying usually in masses overlapping one another but with com- 
paratively slight density. Renal epithelium may be found as 
small, round cells, differing but slightly in size from a leucocyte. 
They may be a little larger, a little smaller, or about the same 
size. They are round and more or less granular in appearance. 

Epithelium from the bladder varies considerably, but the 
majority of cells would properly come under the general head 
of squamous epithelium, rather large and flat with a distinct 
nucleus of medium size. Epithelial cells from the neck of the 



ABNORMAL CONSTITUENTS OF URINE 357 

bladder in male urine are quite typical, being round and com- 
paratively dense with a prominent nucleus. They are four 
or five times the size of a leucocyte and, in case of irritation 
at the neck of the bladder, are usually present in considerable 
numbers and of quite uniform appearance. 

Renal casts consist of molds formed within the tubules of 
the kidneys which retain the form of the tubules after expul- 
sion into the bladder. According to Ogden the most probable 
theory of their formation is " that they are composed of coagu- 
lable elements of blood that have transuded into the renal 
tubules, through pathologic lesions of the latter, and have there 
solidified to be later voided with the urine, as molds of the 
tubules." Casts are termed blood casts, pus casts, epithelial 
or fat casts according as these elements may adhere with more 
or less profusion to the cast itself. Pure hyaline casts are pale, 
perfectly transparent cylinders, with at least one rounded end 
which can be plainly seen, and may occur occasionally in urine 
from perfectly healthy individuals. Fibrinous casts are highly 
refractive and when seen by white fight are of a yellowish color 
and indicate acute and renal disturbance. Waxy casts re- 
semble the fibrinous casts as regards density, but they have 
no color, and usually indicate advanced and serious stages of 
kidney disease, while the presence of fibrinous casts has no 
necessarily serious significance. 

Blood and Pus are readily recognized under the microscope 
after a very little practice. The blood disks are circular and 
show a characteristic biconcavity in the alternate shading of 
the edge and center by slight changes of focus. The red cor- 
puscles usually show a shade of color by white light. The pus 
corpuscles or leucocytes are larger than the red corpuscles, and 
are granular in appearance. Treatment with acetic acid de- 
stroys the granular matter and brings into prominence the 
cell nuclei, two or three in number. If the leucocytes are free 
and scattered they should not be regarded as pus but be re- 



358 URINE 

ported simply as an excess of leucocytes; if they are very 
numerous and occur in clumps they constitute pus. 

Spermatozoa. — Occasional spermatozoa may be found in 
sediment from either male or female urine and are without 
clinical significance. If persistent and in considerable numbers, 
seminal weakness is indicated (Plate IX, Fig. 2, page 353). 

Fat occurs in urinary 'sediment as small globules, highly 
refractive and varying greatly in size. They are frequently 
adherent to cells or to casts. Fatty casts indicate a fatty de- 
generation, which may or may not result from chronic disease. 
Fat may be demonstrated by staining with osmic acid which 
is reduced by the double-bonded fatty constituent (olein), 
leaving a black deposit which stains the globule. 

Mucin appears in the sediment as long and more or less 
indistinct threads. An excessive amount usually indicates irri- 
tation of some mucous surface. The source would have to be 
detemiined by other more characteristic elements (Plate IX, 

Fig. S)- 

The salts which may be obtained by evaporation of a drop 
of clear urine and detected by the micropolariscope are similar 
to those occurring in the saliva; sodium oxalate is probably 
most frequently found. If the gravity is above normal the 
urea often crystallizes, making it somewhat difficult to pick 
out the abnormal crystalline constituents. Phosphates are 
also usually observed, but these crystals are large and as a rule 
prismatic, not easily mistaken for anything else. 

Recording Results. 
As stated at the beginning of the chapter on urine, our object 
has been the study of this secretion from the standpoint of 
general metabolism, rather than with a view to differentiate 
various forms of renal disease, and while it is important that the 
presence of renal disease should be recognized, its further in- 
vestigation constitutes a proper study for the physician rather 



ABNORMAL CONSTITUENTS OF URINE 



359 



than for the dentist, and when such conditions are found to 
exist a patient's physician should be apprised of the fact. 

Uniformity of method in making out report cards is desirable 
although not absolutely necessary for the best class work; 
hence a few suggestions as to the use of the following blank. 
If no test is made, make no entry whatever on the blank. This 
permits the use of a dash, " — ", to indicate a diminished (less 
than normal) quantity. If a substance is present in normal 
quantity use a capital " N," if increased above normal amount 
use "+." If absent use abbreviation " abs.," never the dash 
or minus sign. Observance of this method greatly facilitates 
correction of the report slips. 



U. No. 


Urine Analysis by 




Name 




Date 




24 h. Am't. 




Urea 


Grams in 24 hours. 
%,= 


Sp. Gr. 


React. 


Uric Ac. 


%,= 


Color 


Appear. 


Ammon. 


%,= 


Ind. 


E. Phos. 


Chlor. 


%,- 


Bile 


A. Phos. 


Phos. Ac. 


%,= 


Diac. Ac. 


Acetone 


Sugar 


%,= 


Alb. 




Uric Ac. to Urea = 


= I to 


Soluble Salts (cryst.) 


Sediment 











360 URINE 

It is often convenient to file analyses by " Case " number. 
This will always be the same and results of urine analyses, 
saliva analyses, physical examination of the patient, diet lists 
and important letters may be brought together forming a com- 
plete story of the case. 

The following saliva blank has been arranged to facilitate 
the comparison of quantities of the sulphocyanates and am- 
monia salts, of albumin and mucin, and of oxidases and nitrites. 
The common algebraic sign of inequality is serviceable here. 

«. ». 



S. S. Date Name 




SALIVA Analysis for 


Appearance Odor Acidity 


Alkalinity 


Spedific gravity Mucin 


Albumin 


Ammonium Salts HCNS 


Ptyalin 


Chlorine Glycogen test 


Phosphates 


Acetone Nitrites 


Oxydase 


Soluble salts by polarized light 


Viscosity 


Sediment 




Remarks : 












CHAPTER XL. 
METABOLISM. 

It has been too much the practice to study a single relation 
and jump at conclusions without regard to co-relation of factors 
which may not appear to be closely allied but which nevertheless 
exert important influences. Witness the effort to establish the 
relationship of tartar deposition to calcium content of the saliva 
without considering the quantity of carbon dioxide present or 
the fact that certain colloidal substances (such as occur in saliva) 
may prevent precipitation of calcium salts. 

The relations of potassium sulphocyanate to dental caries, 
and other problems have been studied in much the same way, 
and the object of this chapter is to emphasize the necessity of 
getting all possible viewpoints of a given question before attempt- 
ing to draw positive conclusions regarding it. 

It is conceded that the general systemic condition may be an 
important factor in the success of oral treatment by the dentist. 
In other words it is worth while to know something of the general 
condition of the patient in addition to the knowledge obtained 
by the local examination. 

Metabolism is an inclusive term indicating the chemical 
changes whereby the body utilizes the nutritive elements of the 
food. It may be considered in two divisions as constructive 
metabolism, anabolism, or synthetic processes, and destructive 
metabolism, catabolism, or analytic processes. 

We have studied the cleavage of complex food molecules as 
carried on by the digestive processes but they are here by no 
means complete. How far the cell carries analysis of digestive 
products is unknown, possibly to very simple forms, but we know 
that the analytical process is continued and subsequently exten- 

361 



362 METABOLISM 

sive and complex syntheses result in the building and repair of 
tissue. The food material upon which tissue building and heat 
production depend may be classified as of four kinds, Protein, 
Fat, Carbohydrates, and Mineral Salts. 

In considering the utilization of these substances by the 
system we are obliged to content ourselves with a very general 
outline and a few definitions. We have suggested the dual 
nature of metabolism resulting in the maintenance of heat and 
repair of tissue, but we have come to accept the measure of food 
value as expressed in terms of heat production alone. This 
method may not be ideal but as yet we have no unit of value 
which will measure the usefulness of all four kinds of food ma- 
terial. The unit generally used is the calorie, which may be 
defined as the degree of heat necessary to raise one kilo of water 
one degree centigrade, and is a thousand times as great as the 
small calorie (seldom used). 

The combustion of one gram of fat furnishes a heat equivalent 
of nine and three tenths calories, while a gram of either pure 
carbohydrate or protein will furnish four calories. These figures 
are not absolutely accurate because of slight discrepancies be- 
tween the combustion of metabolism and the combustion of the 
colorimeter but they are accepted as the basis for computation. 

An average adult male doing average work neither wholly 
sedentary nor wholly muscular will require perhaps 2500 calories 
per day. This should be made up of a "balanced" diet consist- 
ing approximately of eighty grams of protein, one hundred and 
twenty grams of fat and three hundred grams of carbohydrates. 
The digestibility and adaptability of food should also receive 
careful attention, but as this is largely a matter of individual 
peculiarities tables and rules are impractical. As an illustration 
of this fact take salt pork and bacon containing similar percent- 
ages of fat, and yielding about the same number of calories, but 
the one is very indigestible, the other is often used in the diet 
of invalids or small children. 



METABOLISM 363 

The calorie requirement per kilo of body weight for an adult 
doing average work is about thirty-five, for children it is much 
greater than this. 

Fat. — The fat molecule does not necessarily undergo decom- 
position (cleavage) to the same extent as either the protein or 
carbohydrate molecule; that is, albumin of the egg must be 
resolved to very simple forms and a new albumin molecule be 
built up before it can be absorbed and utilized, while fat from 
one animal can be recovered as such from the tissues of another; 
the second having used the first for fopd. 

According to Taylor (Digestion and Metabolism) the mole- 
cule of stearic acid passes through various acids of the series, the 
chain splitting each time at the beta carbon till butyric acid is 
reached. From this point the catabolism proceeds, in part, in 
the same way as before resulting in formic acid, C0 2 and H 2 0, 
but from butyric acid we may also obtain the beta oxybutyric 
acid, diacetic acid and acetone. Normal fat metabolism is 
dependent upon the simultaneous metabolism or combustion of 
carbohydrates, that is, the absence of carbohydrates results in 
acidosis due to imperfect oxidation of fat and consequent forma- 
tion of the acetone bodies. 

Protein metabolism results in the splitting of the complex 
protein molecule with the formation of amino acids. Some of 
these such as glycerol, alanin and aspartic acid are capable of 
producing carbohydrates, others like tyrosin and histidin are not. 
The cleavage of some amino acids splits off urea, but in a much 
larger number of cases such cleavage results in the formation of 
ammonia which then unites with water and carbon dioxide 
forming urea. 

Carbohydrates. — The present concept of carbohydrate metab- 
olism is given by Dr. Percy G. Stiles in the Boston Medical and 
Surgical Journal for April, 191 7. From this article we abstract 
the following brief conclusions: 

Carbohydrates after digestion and absorption are found in 



364 METABOLISM 

the blood stream as blood sugar (glucose) . This sugar is oxidized 
by the muscles, resulting in the production of lactic acid, the 
presence of which causes fatigue. During relaxation this lactic 
acid is reincorporated in an undetermined "precursor" which 
had been responsible for its production in the first place. 

Concerning the role of the pancreas in carbohydrate metab- 
olism Stiles says, "A function of this organ even more necessary 
than its digestive contribution is the delivery to the blood of the 
hormone which makes it possible for the muscles, including the 
heart, to oxidize sugar. Abundance of this hormone insures a 
high tolerance for sugar; want of it produces, according to the 
degree of the lack, a low tolerance or substantial inability to make 
use of carbohydrate." 

Mineral Salts. — A well-balanced diet will furnish the proper 
amounts of mineral solids (excepting perhaps sodium chloride) 
but all diets are not balanced and it is well to know what part the 
various salts have in maintaining the health of the individual. 

Sodium chloride is essential to digestion because it has been 
repeatedly demonstrated that if sodium chloride is withheld 
hydrochloric acid will not enter the stomach. Excess of sodium 
chloride may cause irritation or place an undue strain upon weak 
or diseased kidneys and in such cases should be avoided; on the 
other hand acidosis usually results from a salt-free diet. 

Potassium salts are said to keep the tissues soft and pliable, 
to prevent hardening of the arteries, etc., but potassium salts 
may cause a diminution of necessary sodium according to 
Bunge (Physiologic and Pathologic Chemistry, 2nd Edition), 
who says that potassium salts will react with sodium chloride 
in the system forming potassium chloride and undesirable sodium 
salts, both of which are eliminated by the kidneys and thus cause 
loss of sodium. 

Tibbies quotes Cahn in Zeit. f. Physiol. Chem. in practically 
the same statement. 

Calcium salts in considerable quantities are essential during 



METABOLISM 365 

childhood and in fact as long as calcification of any sort is a 
necessary process (as in pregnancy) . In old age the system needs 
but little calcium. Tibbies says that daily diet should include 
one to one and one-half grams of calcium oxide, and care should 
be taken that it is not lost as oxalate. 

H. C. Hartwig in the International . Journal, of Orthodontia 
finds a direct relationship between the calcium content of the 
saliva and caries in pregnant women. Cosmos 191 7, page 665. 

Magnesium occurs generally distributed in the system, the 
bones containing about one per cent. By increasing the amount 
of magnesium ingested the percentage in the bone may be 
increased but it does not take the place of calcium. The com- 
pounds of magnesium are generally more soluble than those of 
calcium. Magnesium oxide, as milk of magnesia, is used exten- 
sively as an antacid. An excessive amount, however, may act 
in removing necessary calcium in just the same way that potas- 
sium acts in removing sodium, as indicated by the following from 
Pickerills' Prevention of Dental Caries and Oral Sepsis, page 120. 

"Weiske's experiments also support these findings. For 
instance, of two rabbits, one received one gram CaC0 3 daily in 
addition to its food; the other one gram of MgC0 3 for three 
months.^ The rabbits were then killed, and it was found that, 
although they were of equal body-weight, the total weight of 
the bones (dried and fat-free) in the first rabbit exceeded that of 
the second rabbit (77.45 grams : 69.52 grams) ; and, further, that 
the amount of organic matter in the bones of the MgC03 rabbit 
was in excess of that in the CaCOs rabbit." 

Iron is an essential constituent of blood derived from food, 
and perhaps more than in the case of any other mineral con- 
stituent, it is necessary for iron to be taken in natural organic 
combination. 

Phosphates are essential for the development of all cellular 
tissue. Phosphates are credited with preventing the deposition 
of uric acid by the reaction on page 242, also with keeping 



366 METABOLISM 

calcium oxalate in solution. Phosphate acts beneficially in the 
bowels by slightly stimulating the peristaltic action. 

Iodine occurs in the ductless glands, and is apparently 
necessary for their best development, although this fact has been 
seriously questioned. 

It is impracticable to give tables of food composition, but the 
following may be noted: 

Strawberries, beans and potatoes are rich in potassium 
compounds; beets, spinach, turnips and cherries are rich in 
sodium salts; milk, oranges, turnips and parsnips are rich in 
calcium oxide; almonds and walnuts are rich in mangesium 
oxide; carrots and rice are rich in iron; meat, cheese, beans, 
eggs and wheat are rich in phosphates; coca powders, rhubarb, 
and spinach, are rich in oxalates. 

Vitamines. — In regard to these substances we quote again 
from Doctor Stiles: "Five years ago the emphasis in this sphere 
(the field of nutrition) was upon the variable value of proteins 
from different sources. It appears largely to have shifted to the 
importance of minor constituents of the diet. The view that 
beriberi, scurvy, and perhaps pellagra are deficiency diseases, 
in the sense that they are caused by the failure of the food to 
provide certain specific compounds which are required for normal 
maintenance, is generally familiar. It was at first proposed to 
describe these essential substances as vitamines. The term 
would imply that they were nitrogenous and of a fixed molecular 
type. It has been thought better to call them merely accessory 
substances. This does not commit one to any narrow conception 
of their chemical nature." 



EXPERIMENTS. 

EXPERIMENTS FOR CHAPTER I. 

If possible it is highly desirable to spend a little time in 
reviewing the principles which form a necessary foundation for 
any kind of chemical specialization. These are supposed to have 
been studied in High School course, but in the author's experi- 
ence many students enter upon the study of dentistry not 
directly from High School graduation but after a lapse of one, 
two, or more years. Hence a few experiments are introduced 
suitable to accompany such a lecture review as suggested above. 

Oxidation and Valence. 

Exp. i. Weigh carefully a porcelain crucible. Then weigh 
into it about one gram of clean copper turnings. Heat strongly 
for about fifteen minutes; then cool and weigh. Explain in- 
crease of weight and compare result obtained with theoretical 
result, assuming that the entire amount of copper had been 
oxidized. 

Exp. 2. To a solution of potassium chlorate add a little 
sulphurous acid and boil. Test the sulphurous acid for sul- 
phuric acid (H2SO4) before starting and after completing the 
experiment. 

Exp. 3. Prepare some chlorine water as follows: Into a 
test-tube drop some crystals of KCIO3. Add a few c.c. of strong 
HC1, just enough to cover the crystals. Allow the evolution of 
gas to become fairly brisk and fill tube three-quarters full of 
water. 

KCIO3 + 2 HC1 = KC1 + CI + C10 2 + H 2 0. 

Caution. Avoid heating, as in this reaction oxides of chlorine 
are formed which are liable to explode if heated. 

367 



368 EXPERIMENTS 

Avoid the escape of CI gas into the laboratory as far as 
possible. 

Exp. 4. Warm a little sulphurous acid solution with a few 
drops of the chlorine water just prepared, testing for H 2 S0 4 as 
in Exp. 2. 

Exp. 5. To a dilute solution of potassium ferrocyanide add 
some strong chlorine water, and warm. After ten or fifteen 
minutes test for the presence of ferrocyanide with dilute ferric 
chloride. Explain. 

Crystallization and Solution. 

Exp. 6. Make hot, nearly saturated solutions of each of the 
following: potassium bichromate, sodium chloride, potassium 
nitrate. Turn off, or filter, the clear, hot solutions and allow to 
cool. When they have nearly reached the room temperature, 
again decant the clear solutions and place in ice water until 
thoroughly cold. Compare the effects of the temperature on 
the solutions of the three salts. 

Exp. 7. Wrap a few crystals of KMn0 4 in a piece of filter 
paper and suspend in the top of a test tube-full of water. Infer- 
ence regarding gravity of solution? 

Exp. 8. Mix equal volumes of ether and water in a test-tube. 
Shake gently, allow to separate completely. Remove a portion 
of the ether and test for water with anhydrous CuSCX 

Exp. 9. Into the 25 c.c. graduate in your desk, measure as 
accurately as possible 15 c.c. of alcohol. Into a second graduate 
measure in like manner 10 c.c. of water and add it slowly to the 
alcohol in the first graduate. Stir carefully with a glass rod. 
Xote change in temperature if any. Note volume of mixed 
liquids and explain. 

Exp. 10. In a test-tube dissolve a small crystal of iodine in 
one or two cubic centimeters of alcohol. Note color of solution. 
Add ten cubic centimeters of water and explain appearance of 
the iodine solution. Now add five to ten cubic centimeters of 






OSMOSIS AND DIALYSIS 



369 



chloroform, close tube with thumb and turn over several times. 
Explain results. 

Osmosis and Dialysis. 

Exp. 11. The student may satisfactorily demonstrate 
osmotic pressure for himself by the use of the following experi- 
ment: 

Prepare a substitute for the usual semipermeable cup by 
taking the ordinary dialyser parchment tubing. Soak first in 
warm water and then in a dilute solution (2%) of potassium 
ferrocyanide. Allow to become nearly dry and then soak in a 
dilute solution of copper sulphate. Allow the tube to become 
nearly dry again, then wash once or twice with warm water. 

With dialyser tubing thus prepared, a small bag 
or pouch capable of holding 10 or 15 c.c. can be made 
and tied very tightly to one end of a piece of glass 
tubing four or five inches long with an internal 
diameter of three or four millimeters. 

Fill the parchment bag with sugar solution and then 
introduce a previously selected capillary tube which 
fits into the larger tube rather closely. Seal joints A 
and B (Fig. 33) with paraffin and suspend the bag in 
a beaker of distilled water. Watch the level of the 
liquid in the capillary tube. 

Exp. 12. In a dialyzing tube (Fig. 26, page 316) 
place a solution of NaCl. In another dialyzing tube 
place a solution of egg albumin; set the tubes in 
separate small beakers of distilled water. After 
several hours standing test the distilled water in the 
first beaker for salt by adding a little silver nitrate solution, 
and test the water in the second beaker for albumin by boiling 
with a drop of acetic acid. Compare results of these tests 
with similar tests made with known solutions of salt and of 
albumin. 




Fig. 33.' 



370 EXPERIMENTS 

Neutralization and Hydrolysis. 

Exp. 13. Add a dilute solution of caustic potash to 5 c.c. 
of nitric acid diluted with twice its bulk of water, until the 
mixture turns litmus paper neither red nor blue. Without 
boiling evaporate the solution in a porcelain dish. Test with 
glass rod until a drop hardens as it cools, and becomes almost 
solid. Then let entire solution become cold. 

Note three differences in the substance produced by this 
experiment from either of the original substances used. 

Write in your laboratory notebook the following neutraliza- 
tion reactions : 

1. Ammonium hydroxide and nitric acid. 

2. Sodium hydroxide and nitric acid. 

3. Ammonium hydroxide and oxalic acid. 

4. Sodium hydroxide and oxalic acid. 

5. Sodium hydroxide and nitrous acid. 

Exp. 14. Rose's Reaction.* — Color a solution of borax, 
(M/10) with litmus solution, then add acetic acid very carefully 
till the litmus just turns pink. Now dilute largely by turning 
into distilled water when the color again becomes blue due to 
increased hydrolyzation of the borax. 

Exp. 15. Place 2 c.c. of M/10 solution of borax in each of 
two small beakers, add to one a few drops of HgNOs, and to the 
other a few drops of AgN0 3 solution. Note the color of the 
precipitate in each case. 

In each of two larger beakers place 50 c.c. of water with five 
or six drops (1/2 c.c.) of the above borax solution, then to one 
add a few drops of HgN0 3 solution, and to the other some AgN0 3 
solution till a precipitate is produced. Note color of precipitate 
in each case (Hg 2 and Ag 2 are produced). 

Now dilute the mixture in the first two beakers (containing 
precipitate of borates) with 50 c.c. of water. Stir and allow to 

* Holleman-Cooper, Inorganic Chemistry. 






PEROXIDES 371 

stand ten minutes. Draw inference regarding hydrolysis of 
borax, also regarding relative stability of the borates of silver 
and mercury. 

Equilibrium and Ionization. 

Exp. 16. To 5 c.c. of a tenth molar solution of ferric chloride 
add 15 c.c. of a tenth molar solution of KCNS. Dilute a portion 
of the red solution thus produced with distilled water until only 
a faint yellow color remains. Divide this nearly colorless solu- 
tion into four parts. To one add 2 or 3 c.c. of ferric chloride, to 
the second, about twice as much of the KCNS originally used, 
to the third, add one-half its volume of M/10 solution of KCL 

Compare portions 1 and 2 and explain how this experiment 
shows the law of chemical equilibrium. 

Explain also how it illustrates ionization of ferric sulpho- 
cyanate and why it is necessary to use more of the KCNS than 
of the FeCl3 solution to get approximately the same depth of 
color. 

Now compare 3 and 4 and explain how these solutions show 
the reversible character of the reaction between FeCl3 and KCNS. 
Do portions 3 and 4 illustrate law of mass action? 

Peroxides. 

Exp. 17. Prepare a solution of peroxide of hydrogen as 
follows: Add to 10 or 15 grams of Ba0 2 enough water to make 
a paste and allow to stand about half an hour. Then add 20 or 
30 c.c. of a ten per cent, solution of H 2 S0 4 . Stir thoroughly and 
after five minutes filter off the solution and test for H 2 2 . (Test 
given on page 181.) 

The half hour treatment with water serves to hydrate the 
Ba0 2 and makes the action of the acid much more rapid. 

What is the white solid remaining on the filter paper? 

Complete Ba0 2 + H 2 S0 4 = 

Exp. 18. Dissolve peroxide of sodium in dilute HC1 leaving 
the reaction faintly acid. Dissolve also a little peroxide of 



372 EXPERIMENTS 

sodium in water and compare the bleaching properties of the two 
solutions. 

Exp. 19. To a solution of H 2 2 add a little KI solution, then 
add about 5 c.c. of chloroform. Shake well. Set aside for a 
few moments then examine and explain result. 

Exp. 20. Dissolve a very little sodium perborate, NaB0 3 .- 
4 H 2 0, in a little warm water and test the solution for H 2 2 with 
potassium bichromate, sulphuric acid and ether as on page 181. 

LABORATORY WORK LN QUALITATIVE ANALYSIS. 

During the study of qualitative analysis the preliminary work 
for each group, which may consist in confirming the statements 
given in the text regarding the formation of precipitates and 
properties of the same, should be carried out prior to the analyses 
of unknown solutions. In addition the following experiments 
may be used. 

Experiments with metals of Groups I and II. 

Exp. 21. Precipitate a little silver chloride according to the 
following : 

AgN0 3 + NaCl = AgCl + NaN0 3 . 

Filter and allow the precipitate to become nearly dry. Mix a 
little of the precipitate with powdered charcoal, and heat be- 
fore the blowpipe until a globule of metallic silver is obtained. 

Exp. 22. Mix intimately a small quantity of litharge and 
powdered charcoal. Heat in a blowpipe flame and obtain a 
particle of metallic lead. 

Exp. 23. In a solution of lead (acetate or nitrate) suspend 
a strip of zinc. Set aside for several hours and note the sepa- 
ration of metallic lead. Write the reaction. 

Exp. 24. Put a small quantity of cinnabar (HgS) into a 
small, hard glass tube open at both ends. Hold the tube, slightly 
inclined, in a strong heat of the Bunsen flame; then examine the 
sublimate under the microscope. What becomes of the sulphur? 



ALUMINIUM, CHROMIUM AND IRON 373 

Exp. 25. Hold a strip of iron or steel (knife blade) for a 
few seconds in a solution of copper sulphate. Does the strip of 
iron dissolve? If so, in what combination? 

Exp. 26. In an open, hard glass tube, heat strongly a mix- 
ture of charcoal and copper oxide. Explain the change of color. 

Exp. 27. To a very small piece of copper foil in a test-tube, 
add a little ammonium chloride solution and allow to stand. 

Aluminium, Chromium, and Iron. 

Exp. 28. (a) To 5 c.c. of dilute alum solution containing a 
little NH4CI, add NH4OH solution and heat. 

Note. — NH4CI aids in the complete separation of the Al 2 (OH) 6 . 

Write reaction. Will the precipitate dissolve in an excess of 
the reagent? 

(b) Repeat, using a chromium solution in place of the alum. 

Exp. 29. Prepare cobalt aluminate according to directions 
given on page 59. This should result in a fine blue color; two 
or three trials may be necessary to produce result. 

Exp. 30. Dissolve a few crystals of FeS04 in water. Filter, 
if necessary, and to a portion of the clear solution add a little 
ammonia water. To another portion add a few drops of HNO3 
and boil for two or three minutes. Carefully add ammonia 
water till a permanent precipitate is obtained. 

To a solution of ferric alum add a little ammonia. What 
change is produced by the HN0 3 in the second part of the 
experiment? 

FeS0 4 + NH4OH = ? 
3 H 2 S0 4 + 6 FeS0 4 + 2 HN0 3 = ? 
Fe 2 (S0 4 ) 3 + NI^OH = ? 

Note. — The addition of sulphuric acid is not necessary to the oxidation by 
HNO3. It simplifies the reaction, as otherwise more or less ferric nitrate is formed. 

Exp. 31. Make a little fresh solution of potassium ferricy- 
anide, also a solution of ferrous sulphate; to the latter add a 
little H 2 S0 4 and a piece of iron wire. After hydrogen ceases to 



374 EXPERIMENTS 

be evolved make the following tests, completing the reaction in 
each case: 

FeS0 4 + KgFeCye = ? Fe 2 Cl 6 + K 3 FeCy 6 = ? 

FeS0 4 + K4FeCy 6 = ? Fe 2 Cl 6 + KjFeCye = ? 

FeS0 4 + KCNS = ? Fe 2 Cl 6 + KCNS = ? 

Exp. 32. To a solution of chrome alum add a little NH4OH. 
Filter, wash the precipitate once or twice and allow to dry. 

Cr 2 (S0 4 ) 3 + NILtOH = ? 

To this dried precipitate add a little dry sodium carbonate 
and potassium nitrate. Mix thoroughly, transfer to a porcelain 
crucible and heat strongly for several minutes, cool and note the 
color of the fused mass. Dissolve in water, acidify with acetic 
acid, and divide the solution into two parts; to the first add a few 
drops of a solution of Pb(N0 3 ) 2 or Pb(C 2 H 3 2 ) 2 , and to the second 
a few drops of BaCl 2 . 

Cobalt, Manganese, Nickel, and Zinc. 

Exp. 33. Add to solutions of Co(N0 3 ) 2 , MnS0 4 , Ni(N0 3 ) 2 , 
and ZnS0 4 a few drops of (NH 4 ) 2 S solution. 

Note color of precipitate and write reaction in each case. 

Exp. 34. On four separate filter papers collect the several 
precipitates formed in Exp. 33. Wash once with H 2 and make 
a borax-bead test with each precipitate as shown in the labora- 
tory demonstration. To each precipitate add, on the paper, 
cold dilute HC1. 

Exp. 35. (a) To a solution of ZnS0 4 add a little NH4OH. 
Will the precipitate dissolve in excess of reagent? 

(b) Repeat, adding NI^Cl before using the NI^OH. 

(c) Repeat (a) using NaOH in place of NH4OH. 

Exp. 36. Precipitate a little MnS, filter and wash. Make 
red-lead test as described at bottom of page 63. 

Exp. 37. (a) To a solution of Co(N0 3 ) 2 in a test-tube, add 



THE ALKALINE EARTHS 375 

a drop or two of dilute NH4OH. Now add an excess of NH4OH 
and note if any change occurs. 

(b) Repeat, using a solution of NiS0 4 . 

What are the precipitates formed? 

Exp. 38. To a solution of zinc salt add a solution of Na 2 C0 3 . 
The precipitate is a basic carbonate of zinc. 

Balance the equation 

ZnS0 4 + Na 2 C0 3 + H 2 = Zn 5 (OH) 6 (C0 3 ) ? + Na 2 S0 4 + C0 2 . 

Exp. 39. Shake in a test-tube a little ZnO and water, filter 
and test nitrate for Zn as in Exp. 33. 

Repeat using ammonium chloride solution instead of the 
water. Inference. 

The Alkaline Earths. 

Exp. 40. To a little clear lime water add a few drops of 
ammonium carbonate solution. 

Ca0 2 H 2 + (NH4) 2 C0 3 = ? 

Will an excess of reagent dissolve this precipitate? If C0 2 
were used in place of (NH4) 2 C0 3 would the solubility of the 
precipitate be the same? Why? 

Exp. 41. Take in separate test-tubes about 5 c.c. of each 
of the following dilute solutions: CaCl 2 , BaCl 2 , Sr(N0 3 ) 2 , and 
MgCk Add to each 1 or 2 c.c. of NH4CI solution, and then a 
little (NH 4 ) 2 C0 3 solution. 

Now add cautiously to each tube, containing a precipitate, 
dilute acetic acid till the precipitates are all dissolved. To each 
of these three tubes add a few drops of K 2 Cr 2 7 solution. 

Write the reactions. Formulate a method for the separation 
of Ca, Ba, and Mg from a mixture containing all three. 

Exp. 42. To a solution of magnesium chloride add a little 
NH4OH and NH 4 C1 solution and lastly some sodium phosphate. 

The formula for the precipitate is NH 4 MgP0 4 . Complete the 
reaction. 

MgCl 2 + Na 2 HP0 4 + NHiOH = 



376 EXPERIMENTS 

Exp. 43. To each of the four solutions used in Exp. 41 add 
a little dilute H 2 S0 4 . 

Which of the four metals forms the least soluble sulphate? 

Which the most soluble? 

Exp. 44. To a solution of Sr(N0 3 )2 add a solution of CaS0 4 
and allow to stand. 

Exp. 45. To a solution of a calcium salt add some ammo- 
nium oxalate solution. W T rite reaction. 

Exp. 46. In a watch glass place a few drops of lime water, 
in another place some baryta water. Set the two glasses aside 
for a while and explain any change that takes place. 

Exp. 47. Make flame tests with solutions of barium, stron- 
tium and calcium. 

The Alkali Metals. 

Exp. 48. In 10 or 15 c.c. of water contained in a porcelain 
dish, dissolve a small piece of metallic potassium. 

Stand well away from the dish as the reaction may result in 
spattering hot water or hot metal. 

Test resulting solution with red litmus paper.* Write reac- 
tion. 

Exp. 49. Take a little strong solution of carbonate of soda 
(about 20% of crystallized salt), heat nearly to boiling in a 
porcelain dish, then add about half as much milk of lime (made 
of one part Ca(OH) 2 to four parts water). Continue the boil- 
ing for several minutes, then allow to settle. Decant the clear 
liquid. 

Test the liquid with various indicators. Is it acid or alka- 
line? 

To a small portion of it add a few drops of HC1. Does it 
effervesce? Test in a similar manner the carbonate of soda 
solution, 

Na 2 C0 3 + CaH 2 2 = ? ' 

* Blue paper may be reddened by leaving it a few hours in a wide-mouth 
bottle after wetting the under side of the stopper with a drop or two of acetic acid 



THE ALKALI METALS 377 

Which of these two compounds used is a base? 

Which an alkali? 

Exp. 50. In separate test-tubes heat the following mixtures: 

1. Solution of NH4CI and solution of NaOH. 

2. Solution of (NH4)2S0 4 and solution of KOH. 

3. Dry NH4CI and dry Ca0 2 H 2 . 

In each case note the odor of the gas evolved and test the 
vapor with moistened red litmus paper and write the reaction. 

Exp. 51. Take three test-tubes and into one put about 
5 c.c. of a dilute solution NaCl; into the second, KC1; and into 
the third, NH4CI; then to each add a few drops of platinic 
chloride solution and allow to stand till the next exercise. 

Exp. 52. Make flame tests according to directions given in 
the lecture room, with salts of sodium, potassium, and lithium. 

Exp. 53. Place in an ignition tube one or two grams of 
potassium tartrate and heat till no further change takes place. 
Cool and dissolve in water. Test a portion of the resulting 
solution with a few drops of HC1. In like manner test the 
original tartrate. 

Note. — In general, the ignition of salts of organic acids results in the for- 
mation of carbonates. 

Exp. 54. Make a spectroscopic examination of solutions of 
Na, K, Li, Ba, Sr, and Ca, and describe the bands observed. 

Note. — This experiment is only to be performed under the direction of an 
instructor. Opportunity will be given for this experiment during the next exer- 
cise if necessary. 

EXPERIMENTS FOR CHAPTER XI. 

Exp. 55. Heat in forceps or on triangle a very small piece 
of each of the following metals, allowing each to fall as it melts 
onto a smooth cold slab (cement floor will do). Return melted 
metals to office for credit. 

Ni-Fe-Cu-Mg-Zn-Cd-Bi-Sn. 



378 EXPERIMENTS 

Study table of melting-points and write your conclusions regard- 
ing the temperature of the Bunsen flame. 

Exp. 56. Fill each of three test-tubes half full of a solution of 
CuS0 4 . Suspend in the first a knife blade; in the second, a 
strip of clean metallic zinc; in the third, a strip of magnesium 
ribbon. Write reactions. 

Exp. 57. Warm gently in a test-tube a little Mn0 2 and HC1. 
Write reactions. Repeat with Pb0 2 and HC1; with PbO and 
HC1. Explain differences in action of the metallic oxides. 

EXPERIMENTS FOR CHAPTERS XH-XIV. 

During the study of Chapters XII-XIV inclusive, the 
student will be required to make qualitative analyses of several 
commercial alloys, dental cements, etc. He will also have to 
prepare and test carefully six alloys, the formulae for which will 
be given on a mimeograph sheet similar to that represented 
on page 379. 

The properties of the various alloys are to be carefully com- 
pared and it is often desirable for two or more students to vary 
a given formula in some one particular and note the result of 
such a variation upon the properties of the amalgam obtained. 



THE ALKALI METALS 

ALLOYS. 
Desk No Name 



379 



Date. 





No. i. 


No. 2. 


No. 3. 


No. 4. 


No. 5. 


No. 6. 


Gold 


















Silver 






1 8 


60 


55 




Tin 


3 


i 


65 


40 


37 








Copper 










4 




Zinc 










4 








Lead 


5 


2 














Antimony 






17 








Bismuth 


8 


4 










Cadmium 




i 

























Nos. 1 and 2 contain lead and must not under any circumstances be made 
in the graphite crucible which you intend to use for silver-tin alloys. These 
are solders or fusible metals. Make 8 to 10 grams and determine melting-point 
of each. 

No. 3 is a very low grade dental alloy. Make 10 grams and test for expansion, 
discoloration, and crushing strength. 

Nos. 4 and 5 are better grade alloys. Make 10 or 12 grams of each. Hand 
one in as sample of work; test the other, annealed and unannealed, as No. 3 was 
tested. 

No. 6, your own formula. Make 15 to 20 grams. Make complete tests 
and also return sample. Return all remaining portions of alloys with desk number 
and composition of the alloy plainly written on envelopes furnished, in order to 
obtain proper credit for the work. 



380 EXPERIMENTS 

CHAPTER XV. 

As part of the work in studying dental cements the student 
is expected to make a mixture of pure zinc oxide and sirupy 
phosphoric acid; then to study the modification of the properties 
of the resulting cement by various additions of insoluble phos- 
phates and magnesium oxide to the acid or powder. He is also 
expected to make qualitative analyses of two commercial cements 
one of which shall be a copper cement. 

chapter xvn. 

Standard solutions are prepared illustrating volumetric proc- 
esses by neutralization, oxidation and precipitation. Numer- 
ous unknown quantitative solutions are given each student for 
practice. 

CHAPTERS XIX AND XX. 

In the study of substances commonly used in dental prepara- 
tions the simpler tests are regarded as important; these have 
been included in the text. If time permits the analysis of a few 
unknown anesthetics, mouth washes and powders will aid 
materially in fixing the composition of this class of substances in 
the student's mind. 

If material is available the analysis of various forms of tartar 
is especially instructive. It will be necessary to use the micro- 
chemical methods suggested in Chapter XVIII for this work. 

ORGANIC CHEMISTRY. 

Experiments with Carbon and Hydrocarbons. 

Exp. 58. Carbon as a decolorizing agent. To 25 or 30 c.c. 
of a dilute solution of aniline color, contained in a small beaker, 
add a teaspoonful of bone charcoal. Heat to the boiling-point, 
rotate or stir thoroughly for a few minutes, and filter. 

Exp. 59. Absorption of metallic salts. To 25 c.c. of solu- 






EXPERIMENTS WITH CARBON AND HYDROCARBONS 381 

tion of lead acetate of such strength that H 2 S water gives marked 
color but no precipitate, add a teaspoonful of bone charcoal and 
treat as in preceding experiment. Test the filtrate with H 2 S 
water and note whether lead has been removed. 

Exp. 60. Perform an experiment with a view to determin- 
ing whether bone charcoal will absorb H 2 S from H 2 S water. 

Exp. 61. Repeat either of the three immediately preceding 
experiments, using wood charcoal in place of bone charcoal. 
Does the wood charcoal work as well as the bone charcoal in 
the absorption of color or other substances? How does bone 
charcoal differ in composition from wood charcoal? 

Exp. 62. Arrange apparatus as shown in Fig. 34. To the 
boiling flask (B) provided with a thermometer registering 200 C. 




Fig. 34. 
connect a beaker condenser, C, immersed in ice water. In this 
apparatus distil slowly 25 c.c. of crude petroleum until at least 
four fractional products are obtained, with boiling points differing 
by at least 15 . Compare the physical properties of the distil- 
lates thus obtained. 

Exp. 63. Charge an ignition tube with dry " marsh-gas 
mixture," found on side shelf (consisting of NaC 2 Ha0 2 , NaOH, 




382 EXPERIMEXTS 

and Ca02H 2 ). Fit with a delivery tube and collect two small 
bottles of the gas over water. 

NaQHA + NaOH = CH4 + Na 2 C0 3 . 

Test the inflammability of this gas. Notice the odor. 

Exp. 64. Mix carefully in a test-tube 2 c.c. of alcohol and 
8 c.c. of strong sulphuric acid. Heat gently and notice odor of 
gas. Fit a bent glass tube to the test-tube and collect over 
water a test-tube full of the gas. To this apply a flame. Note 
the color of the burning gas. 

C 2 H 5 OH - H 2 = QH4. 

Exp. 65. Collect a test-tube full of ethylene (Exp. 64), add 
a few c.c. of dilute permanganate solution and shake. Then 
repeat, using Marsh gas in place of the ethylene (test for un- 
saturated hydrocarbons). 

Exp. 66. Shake together, in separate test-tubes, small 
quantities of petroleum and sulphuric acid in one tube, and 
petroleum and nitric acid in the other. If no action results, mix 
contents of the two tubes and shake again. Explain any change 
or absence of change which may be apparent. 

Exp. 67. In a small generator (see model) place a few small 
pieces of calcium carbide (CaC 2 ), add strong alcohol through the 
funnel tube till the lower end of the tube is " sealed." Now 
add very slowly a little water till a brisk evolution of gas is 
obtained. Collect over water two or three test-tubes full of the 
gas. (Acetylene.) 

Test with a lighted splinter. Note odor of gas cautiously, 
as it is poisonous when inhaled in quantity. 

CaC 2 + 2 H 2 = Ca(OH) 2 + C 2 H 2 . 

Exp. 68. Conduct a little of the acetylene gas into an 
ammoniacal cuprous chloride solution.* What is the red pre- 
cipitate? 

* See appendix for preparation of reagent. This test is characteristic of the 
triple-bonded hydrocarbons. 



EXPERIMENTS WITH CARBON AND HYDROCARBONS 383 

Exp. 69. If the evolution of gas (Exp. 68) has not been 
interrupted the delivery tube may be replaced by a short tube 
drawn out to a fine point and the gas ignited. Note color of 
flame. If it smokes badly, explain the reason for it. 

Experiments with the Halogen Derivatives of the Hydrocarbons. 

Exp. 70. Place in a test-tube a little bleaching-powder, 
cover with strong alcohol and heat the mixture to boiling. 
Notice carefully the odor of the vapor produced and compare 
with a little chloroform (CHCI3) from side shelf. 

4 C 2 H 5 OH + 8 Ca(C10) 2 = 2 CHCI3 + 3 Ca(CH0 2 ) 2 

(Formate of Ca) 

+ 5 CaCl 2 + 8 H 2 0. 

Exp. 71. Heat 1 c.c. of chloroform with about 5 c.c. of 
one per cent NaOH. Test a portion of the resulting solution 
for inorganic chlorides. Distil the remainder of the solution and 
test the distillate, collected in a test-tube, with litmus paper. 

Exp. 72. Place in a test-tube about 1 gram of crystallized 
carbonate of sodium, about half as much iodine and 1 or 2 c.c. of 
alcohol. Now add 10 or 15 c.c. of H 2 and keep the mixture 
at moderate heat (not boiling) till the color of the iodine is dis- 
charged. Allow to cool; collect on a small filter paper some of 
the yellow crystals which have been formed and examine under 
the microscope. What are the crystals? Explain their rela- 
tion to marsh-gas. 

Exp. 73. Prepare ethyl bromide from alcohol, potassium 
bromide and sulphuric acid as follows: Using the apparatus 
suggested for experiment 62, place in the distilling flask about 
30 c.c. of 50% alcohol. Add slowly with constant agitation 
30 c.c. of strong sulphuric acid. Cool thoroughly, then add 30 
grams of powdered potassium bromide. Distil carefully until 
condenser is nearly full of distillate. Pour about a quarter of 
the product into excess of water. Shake well to wash the ethyl 



384 EXPERIMENTS 

bromide. Remove from the wash water by means of a pipette 
and dissolve in a little alcohol. Test this alcoholic solution for 
bromine with alcoholic silver nitrate. 

To another portion of the ethyl bromide add 5 to 10 c.c. of 
alcoholic potassium hydroxide (5% in absolute alcohol). Boil 
for a minute or two, dilute with water and make the usual 
qualitative test for bromides. 

Write reactions. 

Ethyl bromide may also be prepared by distilling a mixture 
of one part of alcohol and five parts of strong hydrobromic acid. 

Exp. 74. Cover one or two small pieces of calcium carbide, 
in a small porcelain dish, with a mixture of three parts water and 
one part alcohol. While the gas is being evolved hold over the 
mixture a test-tube full of chlorine. 

Experiments with Alcohols. (Chap. XXII.) 

Exp. 75. The detection of water in alcohol. Prepare a 
little anhydrous copper sulphate by heating a few crystals of 
CUSO4 on a crucible cover until the water is driven off and a 
nearly white powder results. If this white powder is added 
to half a test-tube full of alcohol, the absorption of water, if 
present, will result in reforming the crystallized salt and a con- 
sequent production of blue color. 

Exp. 76. Water may be separated from alcohol by saturat- 
ing with potassium carbonate. To demonstrate this, take a 
mixture of alcohol and water, containing fifteen or twenty per 
cent of alcohol, and add solid potassium carbonate until the salt 
will no longer dissolve. Agitate and allow to stand. Two layers 
will form, one consisting of alcohol, the other of the water solu- 
tion of K2CO3. 

Exp. 77. To about 75 c.c. of a 10% glucose solution add 
a little yeast and allow to stand for twenty-four hours at a 
temperature of about 37°C; then distil by means of gentle 
heat 10 or 15 c.c, and test distillate for alcohol by iodoform test, 



ALDEHYDES AND KETONES 385 

as given on page 383, Exp. 72. The production of C0 2 may 
also be demonstrated if the gases evolved during the fermentation 
are passed into clear lime water: 

C 6 H 12 6 = 2 C 2 H 5 OH + 2 C0 2 . 

Exp. 78. A test for methyl alcohol. This test is applicable 
only to slight traces of methyl alcohol and may be made with 
a one to two per cent solution or with the first cubic centimeter 
of distillate from the substance suspected of containing methyl 
alcohol. Place 2 or 3 c.c. of very dilute methyl alcohol in a 
test-tube, heat a spiral of copper wire to white heat in a Bunsen 
flame and plunge immediately into the solution to be tested. 
Cool the contents of the tube by immersion in freezing mixture 
or ice water, and repeat the treatment with the hot copper wire. 
Cool again, and a third time introduce the hot copper wire. 
The copper spiral can be made by winding copper wire around a 
lead pencil, and should be of such a length that it is not wholly 
covered by the liquid in the tube. 

This process serves to oxidize a portion of the alcohol to 
aldehyde. Now add to the solution which is being tested a few 
drops of a 1/2% water solution of resorcinol and underlay the 
mixture with strong sulphuric acid. A violet ring will indicate 
the presence of methyl alcohol. The higher alcohols will give 
red or brown rings when similarly treated. 

Exp. 79. Repeat experiment 78, using ethyl alcohol in place 
of methyl alcohol. 

Exp. 80. In 5 or 10 c.c. of absolute alcohol dissolve 1/4 to 
1/2 gram of metallic sodium. Test the gas given off. 

Write reaction. Save the product. 

Exp. 81. Repeat Exp. 57, using allyl alcohol instead of 
ordinary alcohol. 

Experiments with Aldehydes and Ketones. (Chap. XXII.) 

Exp. 82. Mix about 1 c.c. of a very dilute solution of for- 
maldehyde with four or five times its volume of milk in a test- 



$6 EXPERIMENTS 







tube. Keep at a temperature of 40 to 50 C. for half an hour, 
then carefully underlay the mixture with commercial sulphuric 
acid of a specific gravity of 1.80. At the point of contact of the 
two layers of liquid a violet-colored ring indicates the presence 
of formaldehyde. It is necessary that time be allowed for the 
casein of the milk to unite with the formaldehyde, also that the 
sulphuric acid should contain a trace of iron ; this the commercial 
acid usually does. It is undesirable that the acid should be 
stronger than of 1.80 specific gravity; for, if it is, a reddish-brown 
ring may be formed, due to partial carbonization of the casein. 

Exp. 83. To a very dilute solution of formaldehyde add a 
few drops of 1/2% resorcinol solution and underlay the mixture 
with H2SO4 as in Exp. 78. The appearance of a violet ring will 
constitute a test for formaldehyde. 

Exp. 84. To about 5 c.c. of a strong aqueous solution of 
potassium dichromate add a little sulphuric acid, then a few 
cubic centimeters of alcohol, and notice the odor of acetaldehyde 
produced by oxidation of the alcohol. Note also the reduction 
of the dichromate to C^SO^, as follows: 

K 2 Cr 2 7 + 4 H 2 S0 4 + 3 C2H5OH = 

K 2 S0 4 + Cr 2 (S0 4 ) 3 + 3 QaO + 7 H 2 0. 

Exp. 85. Test dilute solutions of acetone, formic and acetic 
aldehydes by Tollen's test for aldehyde as follows: Into a clean 
test-tube which has been rinsed with NaOH solution, place 5 c.c. 
of Tollen's reagent, add 10 c.c. of solution to be tested, shake; 
the silver is reduced, forming a metallic mirror on the inner sur- 
face of the tube. 

To make Tollen's reagent, dissolve three grams of silver 
nitrate in 30 ex. ammonia water and add 3 c.c. of solution of 
sodium hydroxide. 

Exp. 86. Prepare acrolein in each of the following ways: 

1st: From glycerol according to the test given on page 179. 

2nd: Oxidize one or two drops of allyl alcohol with potassium 



EXPERIMENTS WITH ACETONE 387 

bichromate and H 2 S0 4 , similar to the oxidation of ethyl alcohol 
in Exp. 84. 

Exp. 87. To about 5 c.c. of an aqueous solution of chloral 
hydrate add a few cubic centimeters of strong NaOH solution 
and boil. Note odor of chloroform. 

Exp. 88. Isobenzonitril test for chloral or chloroform: 
Place a few drops of a dilute chloral hydrate solution (or a small 
drop of chloroform) in a test-tube, add 5 c.c. of an alcoholic 
solution of alkali hydrate* (NaOH or KOH) and one drop only 
of fresh aniline oil. Heat till the mixture just begins to boil 
and note the odor of the nitril. 

Exp. 89, Test 2 or 3 c.c. of an aqueous solution of aldehyde 
with an equal volume of SchifFs reagent. 

Experiments with Acetone. 

Exp. 90. Preparation of acetone: Heat a few grams of 
dried calcium acetate in an ignition tube, collect the distillate, 
which consists of an impure acetone. If this is mixed with a 
little water and filtered, part of the impurities may be removed, 
and the filtrate tested for acetone by the following experiment. 

Exp. 91. Dilute the filtrate from the last experiment with 
distilled water; add a crystal of sodium nitroprusside. After 
the crystal is dissolved, add a few drops of acetic acid, and then 
an excess of ammonia water. A violet or purple color indicates 
the presence of acetone. Using a dilute solution of acetone in 
place of the alcohol in experiment 72, on page 383, produce iodo- 
form crystals by similar reaction with iodine and sodium or po- 
tassium carbonate. 

Exp. 92. Acetone may be dissolved or mixed with water in 
all proportions; but, upon saturating the water with KOH, 
the acetone will form a separate layer which may be drawn off as 
in the separation of alcohol in experiment 76, page 384. 

* If alcoholic potash or soda is not at hand, the test may be performed with 
5 c.c. of alcohol and 1 or 2 c.c. of a 40% aqueous solution of NaOH. 



388 EXPERIMENTS 

Experiments with Ethers. 

Exp. 93. Into a large test-tube put a little alcohol and about 
half its volume of strong H 2 S0 4 . Warm gently and notice the 
odor. 

Ether is formed by two reactions. First, C 2 H 5 OH + H 2 S0 4 
= C2H5HSO4 + H 2 0. Then the ethyl-hydrogen sulphate 
(C2H5HSO4) is acted upon by a second molecule of H 2 S0 4 , as 
foUows: QH5HSO4 + C 2 H 5 OH = (C 2 H 5 ) 2 + H 2 S0 4 . 

Exp. 94. The production of compound ethers may be dem- 
onstrated by the test for acetic "acid forming ethyl acetate, 
page 100, or by the following experiment used to detect butyric 
acid in gastric contents: 

Exp. 95. Mix in a test-tube 5 c.c. of a dilute (1/2%) solu- 
tion of butyric acid with an equal volume of strong H 2 S0 4 and 
as much strong alcohol. Heat gently and note the odor of 
ethylbutyrate (pineapples). 

Exp. 96. Mix carefully equal portions of cold alcohol and 
strong H 2 S0 4 , about 10 c.c. of each. Then pour the mixture into 
about 200 c.c. of water and add in small portions barium carbon- 
ate in excess. Allow to stand a little, filter and test filtrate for 
barium. Concentrate the solution of barium ethyl sulphate 
thus obtained over a water bath to about half its volume. Then 
mix about 10 c.c. with 2 or 3 c.c. of dilute HC1 and distil. Test 
a portion of the distillate for acid and for S0 4 . Warm the 
remainder with an equal volume of alcohol and note if ether is 
produced. 

Exp. 97. The action of fixed alkalies on compound ethers 
is known as- " saponification." It may be illustrated by heating 
10 c.c. of ethyl acetate with 80 c.c. of a 10% NaOH solution for 
30 to 40 minutes, when the odor of ethyl acetate should be 
destroyed. The flask should be connected with a reflux con- 
denser and the heat applied by immersing the flask in boiling 
water. Write reaction. 



EXPERIMENTS WITH ORGANIC ACIDS 389 

Experiments with Organic Acids (C n H 2n 2 ). 

Exp. 98. Introduce into a small flask (250 c.c. capacity) 
about 30 c.c. of anhydrous glycerin and an equal weight of 
oxalic acid crystals. Boil for several minutes; C0 2 is given 
off and a compound formed between the acid and glycerin; 
then, upon addition of more acid and continued heating, formic 
acid may be distilled. Collect about 10 c.c. of distillate; test 
reaction with litmus-paper. Make silver-mirror test, described 
on page 386, Exp. 85. The silver solution will be reduced, but 
difficulty will be experienced in obtaining the mirror. 

Exp. 99. To 5 c.c. of formic acid solution add 2 or 3 c.c. of 
dilute H2SO4 (1-5) and a little potassium permanganate solu- 
tion; heat the mixture and conduct the gas evolved into a tube 
containing lime water. 

Exp. 100. From a mixture of formic acid, alcohol, and sul- 
phuric acid, ethyl formate may be evolved in a manner similar 
to that in the production of ethyl acetate (page 100). Compare 
the odors of these two ethers. 

Exp. 101. To a dilute aqueous solution of acetone add 
potassium permanganate slowly until the mixture is perma- 
nently colored pink; filter, add dilute sulphuric acid and distil 
until 1 or 2 c.c. of distillate are obtained. This may be tested 
for acetic acid by litmus paper and ferric chloride. 

Exp. 102. To a dilute solution of ferric chloride add a little 
acetic acid; divide the solution into two parts; to one add mer- 
curic chloride and to the other HC1, and note results. 

Exp. 103. Repeat Exp. 102, using diacetic acid in place of 
acetic. 

Exp. 104. Repeat Exp. 102, using meconic acid* in place of 
acetic. 

Compare results of these three experiments and save record 
for future use in the study of saliva. 

* Laudanum diluted with water till color is light brown may be used. 



390 EXPERIMENTS 

Exp. 105. In a small flask saponify a little butter by heating 
with alcoholic potash over a steam bath till mixture is dry. 
Dissolve in water, add dilute H 2 S0 4 , and distil off a portion of 
the butyric acid. Record whatever can be learned from this 
experiment regarding the physical properties of the butyric acid. 

Exp. 106. In separate test-tubes take about 5 c.c. of solu- 
tions of stearic and oleic acids in carbon tetrachloride. Add to 
each about 1 c.c. of a one-tenth per cent solution of iodine also 
in carbon tetrachloride, allow to stand for some time, and 
explain fully the difference in action exhibited by the two fatty 
acids. 

Experiments with Organic Acids not of the C n H 2n 02 Series. 

Exp. 107. To a dilute solution of permanganate of potassium 
add a few drops of sulphuric acid and heat nearly to boiling. 
Note if any change takes place. Now add a few crystals of ox- 
alic acid and watch carefully. Explain the use of sulphuric acid. 

Exp. 108. In separate test-tubes, insoluble oxalates may be 
produced by adding a solution of ammonium oxalate to a solu- 
tion of (a) calcium chloride, (b) silver nitrate, (c) zinc sulphate, 
(d) copper sulphate, (e) lead nitrate. 

Exp. 109. Place in an ignition tube, fitted with delivery tube 
to collect evolved gas in test-tube, about 3 grams of dry calcium 
oxalate. Heat strongly and test gas evolved with lighted match 
or splinter. After ignition tube has become cold add dilute 
H2SO4 and pass gas evolved into lime water. 

Exp. no. Dissolve about 3 grams of dry oxalic acid (ioo° C.) 
in a test-tube half full of methyl alcohol. It will probably be 
necessary to boil the mixture before solution is complete and 
great care must be used to avoid burning of the alcohol. The 
use of a water bath is recommended. As the hot mixture cools, 
dimethyloxalate will crystallize out. 

Separate sufficient of the crystals to obtain melting-point, 
which should be about 54° C. 



EXPERIMENTS WITH CYANOGEN COMPOUNDS 391 

Exp. in. The ester prepared in above experiment may be 
dissolved in alcohol and upon addition of NH 4 OH will give a 
precipitate of oxamide. 

Exp. 112. Take a test-tube half full of calcium chloride 
(10%), make strongly alkaline with NH4OH and pass C0 2 into 
the mixture for several minutes. A solution of calcium carbon- 
ate will result. 

Write reaction, CaCl 2 + 2 C0 2 + 4 NH4OH = ?. Heat the 
solution of calcium carbonate just produced till a precipitate of 
CaC0 3 is produced. 

Write reactions showing the formation of CaH 2 (C0 3 )2 and the 
precipitation of CaC0 3 from the acid salt. 

Exp. 113. To 1/3 test-tube of cider vinegar add a few cubic 
centimeters of basic acetate of lead solution; a bulky precipitate 
of lead malate separates. 

Exp. 114. Dilute a few drops of neutral ferric chloride solu- 
tion until no color is discernible, then to 10 c.c. of this dilution 
add 4 to 5 drops of 1/2% solution of lactic acid. A greenish- 
yellow color constitutes a positive test. 

In practical application of this test, it needs further con- 
firmation by boiling the unknown solution with a drop or two 
of HC1 and then extracting with ether. Evaporate the ether, 
take up the residue in 2 or 3 c.c. of water and repeat the test 
as given above. If the yellow color persists, it is due to lactic 
acid. 

Experiments with Cyanogen Compounds. {Chap. XXV.) 

Exp. 115. In a large test-tube dissolve one half gram or less 
of potassium ferrocyanide in about 4 c.c. of water. Add a little 
H 2 S0 4 and boil, conducting the gas evolved into a beaker con- 
denser (Fig. 35) by means of a bent glass tube. Note the odor 
of this dilute solution. (Do not smell of the contents of generat- 
ing tube, as the strong acid is intensely poisonous.) Write 
reaction. 



392 EXPERIMENTS 

Exp. 116. To one half of the dilute hydrocyanic acid 
prepared in the previous experiment add a drop or two of 
AgN0 3 solution with a little HN0 3 . After the precipitate 
has settled, decant the fluid, then add an excess of ammonia 
water. 

Exp. 117. To the other half of the HCN from Exp. 115 add 
a little solution of ferrous sulphate; also a few drops of ferric 
chloride solution; then a little KOH solution; mix thoroughly 
and acidify with HC1. A blue precipitate, Fe 4 (FeCy 6 ) 3 , is a test 
for HCN or any soluble cyanide. 

Exp. 118. To a few drops of KCN solution add a little 
yellow ammonium sulphide, (NEL^S, and evaporate to dryness. 
Dissolve in water; acidify with HC1 and add Fe 2 Cl6 solution. 

Exp. 119. In a small flask boil a solution of KCN. While 
boiling, test the vapors for ammonia gas. Solution of potassium 
formate remains in the flask. 

Complete reaction, KCN + 2 H 2 = ?. 

Exp. 1 20. To a little dilute (2%) solution of K4Fe(CN) 6 add a 
little bromine water and boil. Prove the formation of KsFe(CN) 6 
by use of FeCl 3 . 

From this experiment what is the relative valence of iron in 
the two compounds? Why? 

Exp. 121. To a fresh solution of K 3 Fe(CN) 6 add a little 10% 
KOH solution and some PbO, shake and filter. To the clear 
filtrate add FeCls- 

Give reason for the statement that the PbO has acted as a 
reducing agent. 

Exp. 122. Dissolve a piece of potassium ferricyanide, as 
large as a pea, in 5 c.c. water, add 2 c.c. of a solution of potassium 
ferrocyanide. Dilute to a test-tube full with distilled water and 
put equal amounts of this solution into 2 shell tubes. Examine 
the color through the length of tube, then add to one tube 2 or 3 
drops of strong HC1. Examine again and notice that a trace of 
prussian blue ha^s been produced. Explain. 



UREA AND URIC ACID 



393 



Experiments with Amines and Amides. (Chap. XXVI) 

Exp. 123. Distil 60 c.c. of ammonium acetate in a glass 
retort, as in Fig. 3 5 , fitted with a thermometer. Acetamide should 
distil at about 222 C. and condense as a white solid in the 
receiver. 




Fig. 35. 

Exp. 124. In a 500-c.c. flask place 10 grams of strong, fresh, 
bleaching powder; add 3 grams of acetamide dissolved in 
about 10 c.c. of water. Mix as thoroughly as possible and add 
slowly 25 c.c. of a 20% solution of NaOH. Distil with steam, 
collecting distillate in 15 c.c. of cold water. 

Exp. 125. To a little of the water solution of methyl amine 
prepared in the last experiment add 2 or 3 drops of_ chloro- 
form and a little alcoholic potash. This mixture upon warming 
will give carbylamine. Note the odor. Warm a little of the 
solution with a little 5% NaOH. Test the vapor given off with 
litmus paper and compare with ordinary qualitative test for 
ammonia. 

Urea and Uric Acid. 

Exp. 126. Make separate solutions of 10 grams of potassium 
cyanate* and 8.25 grams of ammonium sulphate. Mix and 

* For method of making potassium cyanate, see Preparation of Reagents and 
Organic Compounds, in the Appendix. 



394 EXPERIMENTS 

evaporate on a water bath in a shallow dish. Separate the 
potassium sulphate as the evaporation proceeds; finally, evapo- 
rate to dryness and extract with absolute alcohol. Evaporate 
alcohol and reserve the urea for subsequent experiments. (See 
Urea, page 237.) 

Exp. 127. Heat a few crystals of urea in a test-tube until they 
fuse and no more gas is given off; cool, and dissolve the fused 
mass in water; add 1 or 2 c.c. of strong NaOH solution, 
then not more than 1 or 2 drops of a 1% CuS0 4 solution. 
Note the pink to violet color produced. This constitutes the 
biuret reaction used in physiological chemistry as a test for 
albumoses and peptones. Biuret is formed from urea as follows : 

/NH 2 

/NH 2 o=c; 
20 = c; = ;nh + nh3. 

X NH 2 = C^ 

X NH 2 

Exp. 128. Produce crystals of urea nitrate and oxalate 
(page 238) and examine under the microscope. Repeat with urea 
obtained from urine. 

This experiment may be performed by concentrating to 
about 1/5 its bulk a little urine and using the concentrated solu- 
tion as a solution of urea. 

Exp. 129. Treat 5 c.c. of urea solution (urine may be used) 
with a little sodium hypochlorite or hypobromite; note results 
and study reaction given on page 238. 

Exp. 130. Heat one- third of a test-tube of urine with barium 
hydroxide (baryta-water) ; test vapor with red litmus for NE^. 

Exp. 131. Murexide test for uric acid: Place a very small 
quantity of uric acid on a porcelain crucible cover, or in a small 
evaporating dish. Add 2 or 3 drops of strong nitric acid 
and evaporate to dryness over a water-bath. A yellowish-red 
residue remains, which changes to a purplish red upon addition 
of a drop of strong NH4OH, and purple-violet upon further 



EXPERIMENTS WITH AROMATIC HYDROCARBONS 



395 



addition of a drop of KOH solution, the color disappearing upon 
standing or upon the application of heat. (Difference from 
xanthin, which also gives a deeper red color.) 

Exp. 132. Repeat No. 131, using caffein in place of uric acid. 

Exp. 133. Heat a little sodium acid urate in a dilute solution 
of NaH 2 P0 4 . Allow to cool, and examine any deposit for uric 
acid crystals. Test reaction of solution both hot and cold 
(page 242). 

Exp. 134. Mix, and allow to stand for some time at reduced 
temperature, 30 c.c. of urine (a 2% urea solution), 2 or 3 c.c. of 
strong Na 2 C0 3 solution, and 5 c.c. of saturated NH4CI solution. 

A precipitate consists of ammonium urate. 

Examine under the microscope and make murexide test. 



Experiments with Aromatic Hydrocarbons. 

Exp. 135. Into a small and thoroughly dry flask (250 c.c.) 
introduce about 50 grams of a mixture consisting of 1 part of 
benzoic acid and 2 parts of quick- 
lime; connect with a beaker con- 
denser (Fig. 36) and heat. Ben- 
zene (benzol) distils over: 

CaO + C 6 H 6 COOH = 

CaC0 3 + C 6 H 6 . 

Exp. 136. Turn a little of 
the benzene prepared in the last 
experiment onto some water 
contained in a porcelain capsule. 
Set fire to it and note that it 
burns with a smoky flame. Cool a few cubic centimeters of pure 
benzene contained in a narrow test-tube by immersion in a 
freezing mixture of ice and salt. 

Exp. 137. In a wide test-tube mix 5 c.c. of concentrated 
H2SO4 with about half its volume of strong HN0 3 ; cool in ice- 




Fig. 36. 



396 EXPERIMENTS 

water or cold running water, and add very slowly about 2 c.c. 
of benzene. Nitrobenzene is formed and may be separated as 
a heavy oily liquid by pouring the mixture into an excess of 
water. Notice the odor of oil of bitter almonds. 

Exp. 138. Observing the same precaution against overheat- 
ing as given in Exp. 137 reduce nitrobenzene to amino-benzene 
as follows: In a large test-tube or small flask place 1 or 2 c.c. 
of nitrobenzene with three times its weight of tin powder. To 
this add 10 or 15 c.c. of strong HC1 in successive small portions, 
keeping cool as indicated. The odor of nitrobenzene should be 
replaced by that of aniline. 

Exp. 139. Heat a mixture of 2 c.c. of aniline, 5 c.c. of water 
and 1 c.c. of strong sulphuric acid to the boiling point; then set 
aside where it may cool slowly. Crystals of aniline sulphate 
will separate. 

Exp. 140. Repeat preceding experiment, using 5 c.c. of 
aniline, 5 c.c. of water and 10 c.c. of strong hydrochloric acid. 
When the mixture has become thoroughly cold filter off the 
crystals of aniline hydrochloride and dry in a current of air. Test 
solubility in water, using only a very little of the crystallized salt. 

Exp. 141. Place 5 c.c. of an aqueous solution of aniline in 
each of three test-tubes. Add to the first a few drops of bromine 
water; to the second a few drops of dilute ferric chloride; and 
to the third a solution of hypochlorite of calcium or sodium. 

Exp. 142. Shake together in a test-tube 1 part of aniline oil 
and 5 parts of water. Is the oil soluble in water? 

Agitate with HC1 added in small portions till liquid becomes 
clear. Explain. 

Exp. 143. To a few cubic centimeters of a 3% phenol solu- 
tion add dilute bromine water. A yellowish-white crystalline 
precipitate of tribromphenol is produced (see page 184). 

Exp. 144. To an aqueous solution of phenol add a few drops 
of solution of ferric chloride. 

Exp. 145. To 5 c.c. of an aqueous solution of phenol add 



EXPERIMENTS WITH AROMATIC HYDROCARBONS 397 

one quarter its volume of ammonia water and then a few drops 
of sodium hypochlorite solution. Mix and warm. A blue-green 
color develops which turns red upon addition of hydrochloric 
acid to slight acid reaction. 

Exp. 146. Repeat Exps. 143 and 144, using an aqueous solu- 
tion of cresol in place of phenol. 

Exp. 147. To a test-tube 1/3 full of nitric acid (50% abso- 
lute HNO3), add, 1 drop at a time, about 1 c.c. of phenol with 
constant agitation. When the phenol has all been added heat 
carefully to boiling. Allow to cool slowly when trinitrophenol 
will be precipitated. 

Exp. 148. Evaporate a few drops of a 1% solution of potas- 
sium nitrate to dryness in a small porcelain capsule. Add 2 c.c. 
of phenoldisulphonic acid;* stir thoroughly, and keep hot for 
three to five minutes; dilute with water, make strongly alkaline 
with ammonia, and note the intense yellow color of ammonium 
picrate. The reaction is used as a test for nitrates in drinking 
water. 

Exp. 149. Determine melting-point of benzoic acid. 

Exp. 150. Arrange two watch glasses of equal size with the 
concave surfaces together and a piece of filter paper stretched 
between them. The glasses may be held together with a small 
brass clamp. 

A little benzoic acid placed in the lower glass may be sub- 
limed by means of a gentle heat through the paper and collected 
upon the upper glass. Examine the sublimate by polarized 
light. See Plate V, Fig. 5, opposite page 204. 

Exp. 151. With an aqueous solution of benzaldehyde deter- 
mine whether Tollen's test for aldehydes (Exp. 85) is applicable 
to aromatic compounds. 

Exp. 152. Boil 10 c.c. of oil of wintergreen with a little of 
20% NaOH; keep the volume constant by frequent addition of 
water. When the oil has entirely disappeared, cool and add HC1 

* For method of preparation of phenoldisulphonic acid, see Appendix. 




398 EXPERIMENTS 

to acid reaction. Salicylic acid will separate, white and crystal- 
line. 

Exp. 153. To a dilute solution of sodium salicylate, or satu- 
rated aqueous solution of salicylic acid, add a few drops of 
Fe 2 Cl6. A slight amount of salicylates in the urine will produce 
this color when a test is being made for diacetic acid (q. v.). 

Exp. 154. Mix in a large test-tube or small flask a little dry 
slaked lime and salicylic acid, connect with a beaker condenser 
(see cut on page 395) and distil. Test distillate for phenol. 
Write reaction. 

Note. — After the first heating, the tube containing the lime and acid may be 
inclined so that any moisture in distillate will run into collecting tube rather than 
back onto the mixture. 

EXPERIMENTS FOR PHYSIOLOGICAL CHEMISTRY. 

Preparation of Oxidase. 

Exp. 155. Clean thoroughly a small potato and grate the 
skin into a small beaker; cover with water and allow to stand 
in a cool place for an hour. Filter through coarse paper. Turn 
about 5 c.c. of the filtrate slowly into 25 c.c. of strong alcohol. 
The enzyme will be precipitated. Filter and test as follows : 

Exp. 156. Transfer the moist precipitate from the above 
experiment into half a test-tube of distilled water. Shake fre- 
quently for about ten minutes and filter. The filtrate will 
contain oxidizing enzymes in solution. Divide the solution into 
two parts; to one add a few drops of tincture of guaiacum, and 
to the other a little of a 1% solution of pyrocatechol. The 
guaiacum gives a blue color, and the pyrocatechol a red-brown 
color in the presence of oxidizing enzymes. 

Experiments with Enzymes. 

Hydrolytic enzymes produce cleavage of the molecule. 
Exp. 157. Take five test-tubes, a-b-c-d-e. Make a thin 
paste by rubbing one-sixth of a yeast cake with water, and place 



EXPERIMENTS WITH ENZYMES 



399 



a little in each of the five tubes; then fill a with a dilute glucose 
solution; b with a dilute solution of milk sugar; c with dilute 
solution of cane sugar; to d add 
a little invertase (an enzyme from 
the mucosa of the small intes- 
tine of a pig) (see Appendix); 
then fill with the same solution 
used for c. Prepare e exactly 
the same as d except that be- 
fore adding the sugar solution 
the enzymes are boiled for at least 
one minute. Fit each tube with 
short delivery tube and allow to 
stand overnight. 

Exp. 158. Take four test-tubes, 
a-b-c-d, arrange as indicated in 
Fig. 37, and half fill each with some 
thin starch paste (see page 430 of 
Appendix). Into a put a little of 
the yeast from last experiment; 
into b a little pepsin solution; into 
c a little saliva (the enzyme of the saliva in ptyalin); into d a 
little invertase as used in preceding experiment. Warm all the 
tubes to about 37 or 38 C, and allow to stand overnight; then 
test contents of each tube for a reducing sugar which may have 
been produced from the starch. (Use Exp. 167.) 

Exp. 159. The student may prepare a fat-splitting enzyme 
(lipase) from an animal source, pig's pancreas, according to 
direction in the appendix; or from a vegetable source, castor 
beans, as follows: 

Fat Digestion with Lipase (Castor Bean). — Grind with the 
powder,* in the order named, 5 c.c. N/10 sulphuric acid, 5 c.c. of 
neutral cotton oil (sp. gr. 0.92) and 5 c.c. lukewarm water. The 

* For preparation of powder, see page 428. 




Fig. 37. 



400 EXPERIMENTS 

water should be added a little at a time and thoroughly worked 
into the mixture so that at the end of the operation a good 
emulsion is secured. Cover the evaporating dish and let stand 
in a warm place overnight. 

Add 50 c.c. of alcohol, 10 c.c. ether, and a few drops phenol- 
phthalein and titrate with N/i sodium hydrate. Calculate the 
amount of fatty acid and the per cent of fat digestion. 

Exp. 160. To one- third of a test-tube of milk, colored slightly 
blue with nearly neutral litmus solution, add half as much 
solution of lipase (fresh pancreatic extract) and keep at about 
40 C. for twenty to thirty minutes. Sufficient fat acid should 
be separated to change the blue litmus to red. Write reaction. 

Exp. 161. Dialyse thoroughly some saliva, using three or 
four changes of water, then see if the effect of dialysis on the 
amylolytic ferment of the saliva is the same as on the amylolytic 
ferment of the pancreatic juice, page 322. 

Experiments with Sugars. 

Exp. 162. Fill a test-tube about one third full of dry straw. 
Cover with 10% hydrochloric acid; boil, collecting the distillate 
in a dry tube. Divide the distillate into two parts, and make 
the following tests for furfuraldehyde which has been produced 
from the pentose contained in the straw. Treat the contents 
of one tube with a little aniline and hydrochloric acid. Red 
coloration indicates the presence of furfuraldehyde. To the 
contents of the other tube add a little solution of casein (skimmed 
milk) and underlay with strong sulphuric acid. Furfurol will 
give a blue or purple line at the point of contact of the two liquids. 

Monosaccharides. — Exp. 163. Test for C and H, using 
cane-sugar. Make closed-tube test for H, which is given off as 
H 2 0, and for C, which remains as such in tube. (See page 105.) 
Write reactions. 

Exp. 164. MoliscKs Test for Carbohydrates. — To a few 
cubic centimeters of a 3% glucose solution add a few drops of 



EXPERIMENTS WITH SUGARS 



401 



an alcoholic solution of a-naphthol, and carefully underlay the 
mixture with strong H 2 S0 4 . 

Exp. 165. To a few cubic centimeters of CuS0 4 solution 
in a test-tube add a little NaOH. Boil and write reaction. 

Exp. 166. Repeat Exp. 165 with the addition of Rochelle 
salt; if solution remains clear on boiling, add a few drops of a 
glucose solution. 

Exp. 167. Fehling's Test for Sugars. — Take about 5 c.c. of 
Fehling's solution* made by mixing equal parts of the CuS0 4 
solution and the alkaline tartrate on side shelf. Boil and add 
immediately a few drops of glucose solution. 
Set aside for a few minutes, watching the results. 

Exp. 168. Repeat Exp. 167, using diabetic 
urine instead of glucose. 

Exp. 169. Repeat Exp. 167 without heat 
and allow to stand for twenty-four hours. 

Exp. 170. 5 c.c. of Benedict's solution (for 
prep, see Appendix). Add 8 or 10 drops of 
a 2% glucose solution. Heat the mixture to 
boiling; keep at this temperature for one or two 
minutes. 

Exp. 171. BarJoeoVs Test. — To about 5 c.c. 
of Barfoed's reagent add a few drops of glucose 
solution; boil and set aside for a few minutes, 
watching results. 

Exp. 172. Fermentation Test. — Fill the 
"fermentation tube" (Fig. 38) found in the desk 
with glucose solution; add a little yeast; insert stopper, with 
long arm of tube extending into glucose mixture nearly to bot- 
tom of tube, and allow it to stand upright, in a warm place, 
overnight. On the next day, test the gas, with which the tube 
is filled, with lime water. 

Exp. 173. Phenylhydrazine Test. — Place about 5 c.c. of 

* For preparation, see Appendix. 




402 EXPERIMENTS 

glucose solution in a test-tube; add an equal volume of phenyl- 
hydrazine solution; keep the tube in boiling water for thirty 
minutes. Allow to cool gradually. Examine the precipitate 
microscopically and sketch the crystals. 

Disaccharides. — Exp. 174. Use dilute solutions of cane- 
sugar, milk-sugar, and maltose, and make on each Fehling's 
test (Exp. 167), Barfoed's test (Exp. 171), and the phenylhy- 
drazine test (Exp. 173). Sketch the different osazone crystals 
obtained. 

Exp. 175. To a dilute solution of cane-sugar add a few 
drops of dilute H 2 S0 4 and boil for five minutes. Cool the 
mixture and make slightly alkaline with NaOH. With this solu- 
tion perform Exps. 167, 171, and 173. Explain results. Com- 
pare with Exp. 174. 

Experiments with Starches and Cellulose. 

Polysaccharides. — Exp. 176. Examine potato, corn, and 
wheat starch under the microscope, use a drop of water and 
a cover glass. Sketch the granules of each in notebook, and, 
while still on the slide, treat with a dilute iodine solution. Note 
changes in appearance of granules. 

Exp. 177. Preparation of starch. Grate a little raw potato. 
Mix thoroughly with water and strain through "bolting" cloth 
or stout coarse muslin. After the liquid has run through, com- 
press the cloth by twisting till no "more liquid can be squeezed 
out. The starch has passed through the cloth and may be 
washed by decantation, dried on filter paper, examined, and used 
for the following experiments: 

Exp. 178. Make some starch paste by rubbing one gram of 
starch to a smooth, thin paste with water; then slowly pour it 
into 100 c.c. of boiling water, stirring constantly. With this 
solution compare a one per cent, solution of dextrine and a solu- 
tion of glycogen * as follows : 

* For the isolation of glycogen, see Appendix. 



EXPERIMENTS WITH FATS AND OILS 403 

(a) Treat each by boiling with Fehling's solution. 

(b) Add to 5 c.c. of each a few drops of tannic-acid solu- 
tion. 

(c) To each solution add a drop of iodine solution. Note 
color of mixture while cold. Heat nearly to boiling and allow 
to cool again, watching the color during process. 

id) To 5 c.c. of each solution add twice its volume of 66% 
alcohol. 

(e) Tabulate results of the tests and formulate method of 
distinguishing these three substances from one another. 

Experiments with Fats and Oils. 

Exp. 179. Test solubility of olive oil in water, ether, chloro- 
form, and alcohol, carefully avoiding the vicinity of a flame. 

Exp. 180. Let one or two drops of an ether solution of the 
oil drop on a plain white paper, also an ether solution of a volatile 
oil found on side shelf. Watch behavior of the two oils, and 
report differences, if any. 

Exp. 181. Dissolve a little butter in warm alcohol, examine 
with the microscope, and micropolariscope the crystals, which 
separate on cooling. 

Note. — If possible perform the next experiment in triplicate, i.e., carry three 
experiments along at the same time using for "fat" the glyceryl ester of the three 
most common fat acids: Olein (lard oil or olive oil), Stearin (beef fat or tallow), 
Palmatin (bayberry wax or tallow, which contains a large amount of free palmitic 
acid). 

Exp. 182. Saponification. — To about two grams of solid fat 
placed in a narrow beaker, or 150-c.c. Erlenmeyer flask, add 10 
or 15 c.c. of alcoholic solution of potassium hydroxide. Allow 
the beaker to stand on the water bath till the alcohol is entirely 
evaporated, then dissolve the resulting soap in water; filter, if 
necessary, to obtain a clear solution and make the following tests : 

(a) Add to a portion of solution a saturated solution of 
sodium chloride. What takes place? 



404 EXPERIMENTS 

(b) To another portion add a few cubic centimeters of a so- 
lution of calcium or magnesium chloride. Explain the results. 

(c) Pour the remainder slowly, and with constant stirring, 
into warm dilute H 2 S0 4 , and heat on the water bath. What is 
the result? Write the equation. Transfer the mixture to a 
filter-paper which has been moistened with hot water, and 
wash with hot water till all H2SO4 is removed. Reserve the 
filtrates. 

Exp. 183. Fatty acids. 

(a) Dissolve a portion of the above precipitates (182 c) by 
warming with strong alcohol. Test the reaction of the solution. 
Examine the crystals, which separate upon standing, with micro- 
scope and micropolariscope. (Plate VII, Fig. 3, page 287.) 

(b) Add to a portion a few cubic centimeters of a strong 
Na2C0 3 solution, and heat till the fatty acids dissolve. Cool. 
What takes place? Explain the reaction. Reserve the jelly. 

Exp. 184. Neutralize the filtrates of Exp. 182 c and evaporate 
almost to dryness on the water bath. Extract with alcohol 
and evaporate. Note the taste. Heat another portion of the 
residue with a little powdered dry KHS0 4 in a dry test-tube, 
and note the odor, which is due to acrolein, CH 2 = CH — CHO. 
Fuse some borax and glycerin on a platinum loop: green color. 

Exp. 185. Emulsification. — (a) Put 1 to 2 c.c. of a solution 
of sodium carbonate (0.25%) on a watch glass, and place in 
the center a drop of rancid oil. The oil-drop soon shows a 
white rim, and a white milky opacity extends over the solution. 
Note with the microscope the active movements in the vicinity 
of the fat-drop, due to the separation of minute particles of oil 
(Gad's experiment). 

(b) Take six test-tubes and arrange as follows: 

1. 10 c.c. of a 0.2% Na 2 C0 3 solution + 2 drops of neutral 

oil. 

2. 10 c.c. of a 0.2% Na 2 C03 solution + 2 drops of rancid 

oil. 



GENERAL PROTEIN REACTIONS 405 

3. 10 ex. of soap-jelly (see 151 b), warm, +. 2 drops of 

neutral oil. 

4. 10 c.c. of albumin solution + 2 drops of neutral oil. 

5. 10 c.c. of gum-arabic solution + 2 drops of neutral oil. 

6. 10 c.c. of water + 2 drops of neutral oil. 

Shake all the mixtures thoroughly and note the results. 
What conclusions do you form relative to the influence of con- 
ditions upon emulsification? 

(c) Examine a drop of an emulsion under the microscope. 

General Protein Reactions. 

Exp. 186. Test dried egg-albumin for C, H, S, and N, ac- 
cording to the methods described on pages 194 and 195. Test 
casein for phosphorus, and dried blood for iron. 

There are several reactions which are common to nearly all 
proteins. For the following tests use a solution of egg-albumin 
(1/50) in water, as a general type of a protein. 

1. Color Reactions. 

Exp. 187. Xanthoproteic Test. — To 10 c.c. of the albumin 
solution add one third as much concentrated HN0 3 ; there may 
or may not be a white precipitate produced (according to the 
nature of the protein and the concentration). Boil; the pre- 
cipitate or liquid turns yellow. When the solution becomes 
cool add an excess of NH 4 OH, which gives an orange color. 
(This color constitutes the essential part of the test.) 

Exp. 188. Millon's Test. — Add a few drops of Millon's re- 
agent* to a part of the albumin solution. A precipitate, which 
becomes brick-red upon heating, forms. The liquid is colored 
red in the presence of non-coagulable protein or minute traces 
of albumin. 

* Mercuric nitrate in nitric acid. For the preparation of this and other re- 
agents, see Appendix. 




406 EXPERIMENTS 

Exp. 189. Piotrowski's Test. — To a third portion add 2 
drops of a very dilute solution of CuS0 4 , and then 5 to 10 ex. 
of a 40% solution of NaOH. The solution becomes blue or 
violet. Proteoses and peptones give a rose-red color (biuret 
reaction) if only a trace of copper sulphate is used; an excess 
of CuSCX gives a reddish-violet color, somewhat similar to that 
obtained in the presence of other proteins. This test responds 
with all proteins. 

Exp. 190. Hopkins-Cole reaction: Mix 2 or 3 c.c. of the 
unknown protein solution with 3 or 4 c.c. of the reagent (gly- 
oxylic acid). Then carefully superimpose upon 5 c.c. of strong 
sulphuric acid in another test-tube. 

The glyoxylic acid is made by the reduction of oxalic acid 
with nascent hydrogen produced by the action of sodium amal- 
gam and water. Formula is CHO.COOH. 

2. General Precipitants. 

Proteins are precipitated from solution by the following re- 
agents (peptones are exceptions in some cases) : 

Exp. 191. Acetic Acid and Potassic Ferrocyanide. — Make 
part of the solution to be tested strongly acid with acetic acid, 
and add a few drops of potassic ferrocyanide solution. A white 
nocculent precipitate is formed (not with peptones) . 

Exp. 192. Alcohol.- — To another part add one or two vol- 
umes of alcohol. 

Exp. 193. Tannic Acid. — Make the solution acid with 
acetic acid, and add a few drops of tannic-acid solution. 

Exp. 194. Potassio-mer curie Iodide. — Make acid another 
portion with HC1, and add a few drops of the reagent. 

Exp. 195. Neutral Salts. — Certain neutral salts precipitate 
most proteins. (NPL^SC^ added to complete saturation to 
protein solutions, faintly acid with acetic acid, precipitates all 
proteins, with the exception of peptones. 



EXPERIMENTS WITH ALBUMIN AND GLOBULIN 407 

Experiments with Albumin and Globulin. 

The albumins and globulins respond to all the general protein 
reactions. Experiments 187 to 195. 

Exp. 196. A specimen of solid egg-albumin, prepared by 
evaporating a solution to dryness at 40 C, is provided. Test 
its solubility in water, alcohol, acetic acid, KOH solution, and 
concentrated HC1. Report results. 

Perform the following additional experiments, using a dilute 
(1/50) solution of egg-albumin. 

Exp. 197. Nitric-acid Test. — Take 15 c.c. of the solution in 
a wine-glass, incline the glass, and allow 5 c.c. of concentrated 
HNO3 to run slowly down the side to form an under layer. 
What other proteins respond to this test? 

Exp. 198. Picric-acid Test. — Take a portion of the albumin 
solution and add a few drops of a solution of picric acid acidified 
with citric acid (Esbach's reagent). What other proteins re-- 
spond to this test? 

Exp. 199. Action of (NH^SO^. — To 10 c.c. of the albumin 
solution in a test-tube add some solid (NH^SC^, shaking until 
solution is thoroughly saturated. Allow to stand a little while, 
shaking occasionally, then filter, saving the filtrate to test for 
albumin by the heat test. Report result. Test the solubility 
of the precipitate on the filter-paper. 

Exp. 200. Action of MgSO±. — Perform an experiment 
similar to Exp. 199 using solid MgS0 4 instead of (NH^SO^ 
With what results? 

Exp. 201. Salts of the Heavy Metals. — Note the action of 
the following: AgN0 3 , HgCl 2 , CuS0 4 , Pb^HsC^. Use solu- 
tions of the salts and of albumin. 

Why is white of egg an antidote in cases of metallic poisoning? 

The following tests serve to distinguish the globulins from 
other proteins. 

The tests may be made upon blood serum, or upon a globulin 



4°S EXPERIMENTS 

(edestin) which may be separated from hemp seed according to 
preparation in Appendix, page 434. 

Globulins. 

Exp. 202. Action of C0 2 . — To 5 ex. of blood serum add 
45 c.c. of ice-cold water. Place the mixture in a large test-tube 
or cylinder, surround it with ice-water, and pass through it a 
stream of C0 2 . A flocculent precipitate (paraglobulin)* will be 
formed . 

Exp. 203. Precipitation by Dialysis. — Into a parchment 
dialyzing tube, previously soaked in distilled water, pour 20 c.c. 
of serum, swing the tube, with its contents, into a large vessel 
of distilled water, which is to be changed at intervals. Let 
stand twenty-four hours, then examine the serum in the dialyz- 
ing tube; it will contain a flocculent precipitate of paraglobulin. 
Give explanation of cause of precipitation. 

Exp. 204. Pour a solution of globulin, drop by drop, into a 
large volume of distilled water (in a beaker). What takes 
place? Explain. 

Exp. 205. Precipitation by Magnesium Sulphate. — Saturate 
about 5 c.c. of globulin solution with solid magnesium sulphate. 
A heavy precipitate will be formed. Compare this with the 
action of the same salt on the egg-albumin solution. Paraglob- 
ulin is so completely precipitated by this salt that the method 
is used for its quantitative estimation. 

Experiments with Keratin and Gelatin. 

Keratins are characterized by their insolubility, and by their 
high content of loosely combined sulphur. 

Exp. 206. Test solubility of keratin (nail or horn) in water, 
acids, alkalies, gastric and pancreatic juices. 

Exp. 207. Warm a bit of keratin with 5 c.c. strong NaOH 

* Paraglobulin is a name applied to the globulin separated from blood serum. 



EXPERIMENTS WITH MILK 4°9 

solution for a few minutes, and add a few drops of a lead acetate 
solution. What is the result? 

Exp. 208. With a solution of gelatin make the usual tests 
for protein. 

Exp. 209. Precipitate gelatin from dilute solution with the 
following reagents : 

(a) Tannic acid. 

(b) Alcohol. 

(c) Acetic acid and potassium ferrocyanide. 

(d) Mercuric chloride. 

(e) Picric acid. 

Experiments with Milk. 

Exp. 210. Examine microscopically whole milk, skim-milk, 
and cream. Note the relative amounts of fat in the three 
varieties. 

Exp. 211. Shake a little cream with chloroform in a test- 
tube; separate the chloroform, evaporate, and melt the fat 
residue obtained; allow it to cool slowly, when fat crystals will 
be obtained, which may be examined under the microscope and 
micropolariscope . 

Exp. 212. With a lactometer take the specific gravity of 
whole milk and skim-milk and explain the difference in results. 

Exp. 213. Test the reaction of milk with litmus. 

Exp. 214. Dilute some milk with six or seven times its 
volume of water, and add acetic acid drop by drop till the 
casein is precipitated. Filter and reserve the precipitate. Test 
the filtrate for proteins, if any remain; determine if possible 
their character. 

Exp. 215. Test another portion of the filtrate for carbohy- 
drates, determining the variety present. 

Exp. 216. To 50 c.c. of milk add a few drops of rennin 
solution; keep at a temperature of 40 C. for a few minutes, 
and explain results. 




410 EXPERIMENTS 

Exp. 217. Take a portion of the precipitated casein from 
Exp. 214, digest at 40 C. with pepsin HC1 for twenty minutes 
or half an hour. While digesting, test other portions of casein, 
for solubility in water, in dilute acid and dilute alkali. Test 
also a portion for phosphorus by boiling in a test-tube with 
dilute nitric acid, cooling to at least 50 C, and adding ammo- 
nium molybdate solution. 

Exp. 218. To a little skim-milk contained in a test-tube add 
a saturated solution of ammonium sulphate. 

Experiments with Mucin. 

Exp. 219. To a solution of mucin* found on the side shelf 
add acetic acid till precipitation takes place. Settle filter, 
wash, and test solubility in water, dilute alkali solution and 
5% HCl. 

Exp. 220. Make color- tests for proteins. 

Exp. 221. Boil a little mucin solution with dilute HCl for 
several minutes. Cool, neutralize, and test for sugar. 

Experiments with Protein Derivatives. 

Exp. 222. Preparation of Metaprotein. — To a solution of 
egg-albumin add a few drops of a 0.5% solution of NaOH, and 
warm gently for a few minutes. With the solution thus ob- 
tained make the following tests: 

Exp. 223. (a) Effect of Heating. — Boil some of the solution 
and report result. 

(b) Effect of Neutralizing. — Add a drop of litmus solution, 
and cautiously neutralize. 

Acid Metaprotein. 

Exp. 224. Add a small quantity of a 0.2% HCl solution to a 
solution of egg-albumin, and warm at 40 C. for one half to one 
hour. Or cover with an excess of 0.2% HCl some meat cut 

* For preparation of mucin solution from navel cord, see Appendix. 



EXPERIMENTS WITH PEPTONES 41 1 

into fine pieces, and expose for a while to a temperature of 
40 C. Filter. With either of the solutions thus obtained 
make same tests as on alkali metaprotein, and compare results. 
How distinguish between them? 

Experiments with the Proteoses. 

Albumoses (Hemialbumose) . — This name includes four closely 
allied forms of albumose, namely: (1) Protoalbumose, (2) 
Deuteroalbumose; (3) Heteroalbumose; (4) Dysalbumose, an 
insoluble modification of heteroalbumose. Commercial peptone, 
which is substantially a mixture of albumoses and peptones, will 
be given out for use. 

Exp. 225. Make a solution of the peptone in water, filter 
if necessary, and saturate with solid (NFL^SO^ Filter. The 
precipitate contains the albumoses, the filtrate the peptones. 
Reserve the filtrate for subsequent tests for peptone. Wash the 
precipitate with a saturated solution of ammonium sulphate; 
dissolve in water, and, with the solution obtained, perform the 
following tests, noting especially the tendency of albumose pre- 
cipitates to dissolve upon the application of heat and to reappear 
upon cooling. 

Using this solution of albumose, repeat Exps. 187, 188, 189, 
197, 198. If no precipitate forms with HN0 3 in Exp. 197, add 
a drop or two of a saturated solution of common salt. (Deutero- 
albumose gives this reaction only in the presence of HC1.) 

Exp. 226. Saturate some of the solution with (NEL^SO^ 
Report the result. 

Exp. 227. To some of the solution add two or three drops of 
acetic acid and then a saturated solution of NaCl. A precipitate 
forms, which dissolves on heating, and reappears on cooling. 

Experiments with Peptones. 
Exp. 228. Using the peptone solution prepared in manner 
above described from commercial peptone, repeat the experi- 
ments indicated in Exp. 225. 




412 EXPERIMENTS 

Exp. 229. Effect of Heating. — Boil some of the peptone 
solution. Report the result. 

Exp. 230. Power of Dialyzing. — Dialyze some of the peptone 
solution. Use 10 c.c. of the peptone solution, and in the outside 
vessel about 100 c.c. of water, which in this case is not to be 
changed. After twenty-four hours test the outside water for 
peptone, employing the biuret test. 

Exp. 231. Action of Ammonium Sulphate. — Saturate some 
of the peptone solution with solid (NH 4 ) 2 S0 4 . Report the result. 

A number of unknown solutions will be given out to be 
tested for carbohydrates and proteins. A report of the results, 
together with the methods employed, is to be made. 

Experiments on Blood. 

Exp. 232. Test the reaction of blood with a piece of litmus- 
paper which has been previously soaked in a concentrated NaCl 
solution. To what is reaction due? 

Exp. 233. Blood-corpuscles. — (a) Examine a drop of blood 
under the microscope. Sketch the red and white corpuscles. 

(b) Note the difference between the corpuscles of mammals 
and those of birds and reptiles. 

(c) Note the effect upon the red corpuscles produced by the 
addition of (1) water, (2) a concentrated solution of salt. 

Exp. 234. Hemoglobin Crystals. — Place a drop of de- 
fibrinated rat's blood on a slide; add a drop or two of water; 
mix, and cover with a cover-glass. Sketch the crystals which 
separate after a few minutes. Or instead of above add a few 
drops of ether to some blood in a test-tube; shake thoroughly 
until the blood becomes "laky," and then place the tube on ice 
till crystals appear. 

Exp. 235. A spectroscope will be found ready for use in the 
laboratory, and the absorption-bands given by oxyhemoglobin 
and hemoglobin will be demonstrated. The student may pre- 
pare solutions for examination as follows: 



EXPERIMENTS ON BLOOD 41 3 

(a) Oxyhemoglobin. — Use dilute blood (one part of de- 
nbrinated blood in fifty parts of distilled water). 

(b) Hemoglobin (reduced hemoglobin) . — Add to blood a few 
drops of strong ammonium sulphide, or one or two drops of 
freshly prepared Stokes's reagent.* Note the change in color 
produced by the addition of the reducing agent. Shake with air 
and note the rapid change to oxyhemoglobin. 

(c) Hemochromogen. — To a little of the hemochromogen, 
reduced with ammonium sulphide, add a few drops of concen- 
trated NaCl, and note the spectrum of reduced hematin or 
hemochromogen. 

(d) Carbonmonoxide Hemoglobin. — Pass a current of illumi- 
nating gas through a dilute oxyhemoglobin solution for a few 
minutes and filter. Note the change of color. Try the effect on 
the solution of (1) ammonium sulphide; (2) Stokes's reagent; 
(3) shaking with air. Note the stability of the compound. 

Exp. 236. Take the specific gravity of blood by filling a test- 
tube one-half full of benzene; add one drop of blood, and then 
add chloroform, a drop at a time, with careful but thorough mix- 
ing, until the drop of blood floats at about the middle of the 
mixture, indicating that the gravity of the mixture and of the 
blood are the same. The specific gravity of the benzene and 
chloroform may be taken in any convenient way. 

Exp. 237. Make the guaiacum test for blood on a sample 
of dried blood; also on potato scrapings. The method is as 
follows: 

To a little clear solution of blood or material obtained from 
potato scrapings, add some fresh tincture of guaiacum; then add 
a few drops of an ethereal solution of hydrogen peroxide, shake 
the mixture and note the blue color obtained. 

From these two tests what do you gather about the value of 

* Stokes's reagent consists of two parts of ferrous sulphate and three parts of 
tartaric acid dissolved in water and ammonia added to distinct alkaline reaction. 
There should be no permanent precipitate. 



414 EXPERIMENTS 

the guaiacum test for blood, and what is probably the cause of 
the coloration? 

Exp. 238. The Benzidine Reaction consists in adding to a 
few c.c. of a saturated Benzidine solution in glacial acetic acid or 
alcohol acidified with acetic acid an equal volume of commercial 
H2O2 and 1 c.c. of the suspected solution. If blood is present 
a green or blue color will develop. It is better to make a blank 
test to insure purity of reagents. 

Exp. 239. Hemin Crystals (Teichrnanrfs Test). — Place a 
bit of powdered dried blood on a glass slide; add a minute 
crystal of NaCl (fresh blood contains sufficient NaCl) and two 
drops of glacial acetic acid. Cover with a cover-glass and warm 
gently over a flame until bubbles appear. On cooling, dark- 
brown rhombic crystals, often crossed, separate (chloride of 
hematin). Similar crystals can be obtained by using an alka- 
line iodide or bromide in place of NaCl. 

Exp. 240. Coagulation of Blood. — Observe the phenomena 
of coagulation as it takes place (a) in a test-tube; (b) in a drop 
of blood examined under the microscope. Explain fully. 

Exp. 241. Proteins of Blood-plasma. — (a) Serum-albumin. 
(b) Serum-globulin. Using blood-serum, separate and identify 
these two proteins. 

(c) Fibrinogen. — Fibrinogen is a globulin found in blood- 
plasma, lymph, etc., together with paraglobulin. Like para- 
globulin it responds to all the general precipitants and tests, and 
in addition gives the reactions with CO2, dialysis, and MgS04- 
It is distinguished from paraglobulin easily by two reactions, viz., 
its power to coagulate, i.e., to form fibrin when acted on by fibrin 
ferment, and its temperature of heat coagulation, which will be 
found to be from 5 6° to 6o° C. 

Exp. 242. Fibrin. — (a) Note its physical properties. 

(b) Note action of 0.2% hydrochloric acid. 

(c) Apply the protein color tests. 



EXPERIMENTS WITH MUSCLE 415 

Experiments with Muscle. 

Exp. 243. Place 25 grams of fresh, finely chopped muscle 
in a beaker with 75 c.c. of 5% solution of common salt, and 
allow to stand for about one hour, with frequent stirring. (In 
the meanwhile perform Exp. 244.) Then filter off the liquid 
and make the following tests with the filtrate. 

(a) Test for proteins. 

(b) Having found proteins, pour a little of the solution into 
a beaker of water. Result. Inference (myosin). 

(c) Make a fractional heat coagulation in the following man- 
ner (upon the care with which the temperatures given are ad- 
hered to, depends the success of the separation) : Warm to from 
44 to 50 C, and keep at that temperature for a few minutes. 
The coagulum is myosin [synonyms: paramyosinogen (Halli- 
burton), musculin (older authors)]. In solutions the myosin, 
which has the properties of a globulin, becomes insoluble after a 
time, because it changes to myosinfibrin. In heating the solu- 
tion as above, a slight cloud may appear at from 30 to 40 C. 
This is due to coagulation of soluble myogenfibrin. Now filter 
off the coagulated myosin. 

Heat filtrate to from 55 to 65 C. The coagulum is myogen 
(synonym: myosinogen). In spontaneous coagulation of its 
solutions it forms, first, soluble myogenfibrin, and, finally, in- 
soluble myogenfibrin. Filter. 

Heat to from 70 to 90 C. Coagulum is serum albumin from 
the blood within the muscle, and is not a constituent of the 
muscle plasma. Filter. 

Test filtrate for proteins. If it shows a slight biuret test, 
this is due either to incomplete precipitation by coagulation 
or to the post-mortem formation of albumose or peptone by 
auto-digestion (autolysis) . 

Exp. 244. Make an aqueous extract of muscle, and test for 
lactic acid by acidulating with H 2 S0 4 , extracting with ether, 



41 6 EXPERIMENTS 

and testing the ethereal extract with very dilute ferric chloride 
solution. The presence of lactic acid is shown by a bright- 
yellow color. 

Experiments with Saliva. 

Exp. 245. Action of Saliva upon Starch. — Take some fil- 
tered saliva in a test-tube and place in the water-bath at 40 C, 
for five or ten minutes. Put some starch paste into a second 
test-tube and place this also in the water-bath for a while, then 
mix the two (10 c.c. of starch paste to 3 c.c. of undiluted saliva) 
and return to the water bath. The starch is changed first to 
soluble starch (if originally a thick paste, it becomes fluid and 
loses its opalescence), then to erythrodextrin, which gives a 
red color with iodine, and finally to achroodextrin, which gives 
no reaction with iodine, and to maltose. Prove these changes 
as follows : Every minute or two take out a drop of the mixture, 
place it on a porcelain plate, and add a drop of iodine solu- 
tion. This gives first a blue color, showing the presence of 
starch; later a violet color, due to the mixture of the blue of 
the starch reaction with the red caused by the dextrin; next a 
reddish-brown color, due to erythrodextrin alone (starch being 
absent), and finally no reaction at all with iodine, proving the 
absence of starch and erythrodextrin. The fluid now contains 
achroodextrin and maltose. Test for the latter with Fehling's 
solution and with Barfoed's reagent. 

Exp. 246. Influence of Conditions on Ptyalin and its Amylo- 
lytic Action. — Report and explain the results of the following 
experiments : 

(a) Boil a few cubic centimeters of the saliva, then add 
some starch paste, and place in the water bath at 40 C. After 
five minutes test for sugar. 

(b) Take two test-tubes: put some starch paste in one, and 
saliva in the other, and cool them to o° C, in a freezing mixture. 
Mix the two solutions, and keep the mixture surrounded by 



ANALYSIS OF GASTRIC CONTENTS 417 

ice for several minutes, then test a portion for sugar. Now 
place the remainder in the water bath at 40 C, and after a 
time test for sugar. 

(c) Carefully neutralize 20 c.c. of saliva with very dilute 
HC1 (the 0.2% diluted), and dilute the whole to 100 c.c. Test 
the action of this neutralized saliva on starch. 

(d) To 5 c.c. of starch paste add 10 c.c. of 0.2% HC1 and 
5 c.c. of neutral saliva, and expose the mixture for a while at 
40 C, and test for sugar. 

(e) To 5 c.c. of starch paste add 10 c.c. of a 0.5% solution 
of Na 2 C0 3 and 5 c.c. of neutral saliva, and expose the mixture 
for a while at 40 C, and test for sugar. 

(J) Carefully neutralize (d) and (e) , and again test the action 
of the two on starch. 

(g) Mix a little uncooked starch with saliva, expose to a 
temperature of 40 C. for a while, and test for sugar. 

Exp. 247. In three separate test-tubes place a few cubic 
centimeters of dilute solutions of KCNS or NH 4 CNS, of meconic 
acid, and of acetic acid; add to each a few drops of ferric chloride, 
and notice that a similar color is obtained in each case. Divide 
the contents of each tube into two portions, and to one set add 
HC1; to the other add mercuric-chloride solution. Formulate a 
method of distinguishing from the sulphocyanates, meconates, 
and acetates. 

Analysis of Gastric Contents and Experiments with Pepsin. 

The following solutions will be found in the laboratory: 

A. A 0.2% Solution of HCl. — This is prepared by diluting 
6.5 c.c. of concentrated HCl (sp. gr. 1.19) with distilled water 
to 1 liter. 

B. A Solution of Pepsin. — Prepared by dissolving two 
grams of pepsin in 1000 c.c. of water. 

C. A Pepsin-hydrochloric-acid Solution. — Prepared by dis- 
solving two grams of pepsin in 1000 c.c. of solution A. 



41 S EXPERIMENTS 

Or, add to 150 c.c. of solution A about 10 c.c. of the glyc- 
erol extract of the mucous membrane of the stomach. 

Exp. 248. Take five test-tubes and label a, b, c, d, e. Fill 
as indicated below. Place in a water bath at 40 C, and ex- 
amine an hour later, and again the next day. 

(a) 3 c.c. pepsin solution + 10 c.c. water + a few shreds of 
fibrin. 

(b) 10 c.c. 0.2% HC1 + a few shreds of fibrin. 

(c) 3 c.c. pepsin solution + 10 c.c. 0.2% HO, and a few 
shreds of fibrin. 

(d) 3 c.c. pepsin solution + 10 c.c. 0.2% HO, boil, and then 
add a few shreds of fibrin. 

(e) 3 c.c. pepsin solution + 10 c.c. 0.2% HC1, and a few 
shreds of fibrin which have been tied firmly together into a ball 
with a thread. 

Make a note of all changes. 

Exp. 249. Filter c. Neutralize with dilute Na 2 C0 3 . Filter 
again. Why? Test the filtrate for the biuret reaction. 

Exp. 250. To 5 grams fibrin add 30 c.c. of the pepsin solu- 
tion and 100 c.c. 0.2% HO. Set in the water bath at 40 C, 
stirring frequently, and leave in the water bath overnight. 
Observe the undigested residue, on the following day, and also 
a slight flocculent precipitate. What is this precipitate? 

Filter and carefully neutralize the filtrate. A precipitate 
varying with the progress of the digestion will form. What is it? 

Remove this by filtration, and saturate this filtrate with 
(NH^SO^ Filter. Save precipitate and filtrate. Of what 
does each consist? 

Exp. 251. Dissolve the last precipitate of Exp. 250 in water, 
and try the following tests: 

(a) Biuret reaction. 

(b) Effect of boiling. 

(c) Test with NH0 3 , as in performing test for albumin in the 
urine, page 344. 



ANALYSIS OF GASTRIC CONTENTS 4*9 

Exp. 252. To the last filtrate of Exp. 250 add an equal vol- 
ume of 95% alcohol, and stir thoroughly. The peptones will 
collect in a gummy mass about the stirring-rod. 

(a) Determine the solubility of peptones in water. 

(b) What is the effect of heat when so dissolved? 

(c) Try the biuret reaction. 

Exp. 253. Demonstration of Rennet Enzyme. — Place 10 c.c. 
of milk in each of three test-tubes. Label the test-tubes 1, 2, 3. 

To 1 add a drop of neutralized glycerol extract of the mucous 
membrane of the stomach (made from the stomach of the calf). 

To 2 add a drop of neutralized glycerol extract, and boil 
at once. 

To 3 add a few cubic centimeters of (NH4) 2 C 2 04 solution, 
and then a drop of a glycerol extract. 

Place these tubes in the water bath at 40 C, and examine 
after five to ten minutes. Explain results in each case. 

Continue heating tube 3 for half an hour, then add 2 or 3 
drops CaCU solution. The liquid instantly solidifies. Why? 

Exp. 254. Digestion of Casein. — Determine the products of 
the digestion of the curd from the last experiment. 

Exp. 255. Tests for Free Hydrochloric Acid. — Try each 
of the following tests with (a) HC1 (0.2%, 0.05%, and 0.01% 
successively); (b) lactic acid (1%); (c) mixtures containing 
equal volumes of (a) and (b). Tabulate the results. 

(a) Dimethylaminoazobenzene. — Use one or two drops of a 
0.5% alcoholic solution. In the presence of free mineral acids 
a carmine-red color is obtained. 

(b) Gunzburg's Reagent. — Phloroglucin, 2 grams ; vanillin, 
1 gram; alcohol, 100 c.c. Place two or three drops of the solu- 
tion to be tested in a porcelain dish, add one or two drops of 
the reagent, and evaporate on a water bath. In the presence 
of free hydrochloric acid a rose-red color develops. 

(c) Boas' Reagent. — This is prepared by dissolving 5 grams 
of resublimed resorcinol and a gram of cane-sugar in 100 grams 



4-0 EXPERIMENTS 

of 94% alcohol. Take three or four drops each of the reagent 
and the solution to be tested, and cautiously evaporate to 
dryness. In the presence of a free mineral acid a rose or Ver- 
million red color is obtained. This gradually fades on cooling. 

(d) Tropceolin 00. — Use one or two drops of a saturated 
alcoholic solution. 

(e) Congo-red. — Use filter-paper which has been dipped into 
a solution of the reagent and then dried. 

Exp. 256. To 5 c.c. egg-albumin in solution add 1 c.c. of 
0.2% HC1. Mix thoroughly, and" test for the presence of free 
HC1. What is the result? How do you .explain it? Repeat 
the test, using a solution of peptone in place of the egg-albumin. 

Exp. 257. Tests for Lactic Acid. — Uffelmann's reagent. 
Mix 10 c.c. of a 4% solution of carbolic acid with 20 c.c. of 
water, and add a drop or two of ferric chloride. 

To 5 c.c. of the reagent add a few drops of the lactic-acid 
solution. Note the canary-yellow color. 

Does the presence of free HC1 interfere with this reaction? 

A more delicate reagent is obtained by adding three or four 
drops of a 10% ferric-chloride solution to 50 c.c. of water. Such 
a solution has a very faint yellow color, which is distinctly in- 
tensified by lactic acid. 

Using 5 c.c. of this nearly colorless solution for each experi- 
ment, note the effect of (a) 0.2% HC1; (b) acid phosphate of 
sodium; (c) alcohol; (d) glucose; (e) cane-sugar. What con- 
clusions do you reach concerning the value of this test, when 
applied directly to the gastric contents? 

The test is best applied to an aqueous solution of the ethereal 
extract of the gastric contents. Add to the contents two drops 
of HC1, boil to a syrup, and extract with ether. Dissolve the 
residue obtained upon evaporation of the ether in a little water, 
and test for lactic acid. 

Exp. 258. Test for butyric acid; see ethyl butyrate, page 215. 

Exp. 259. Test for acetic acid; see acetates (page 100). 



EXPERIMENTS WITH PANCREATIC JUICE 421 

Exp. 260. The acidity of the gastric contents may be deter- 
mined as follows: To 5 c.c. of the filtered contents, diluted with 
25 to 30 c.c. of water in an Erlenmeyer flask, add 2 or 3 drops 
of a solution of dimethylaminoazobenzene. Titrate with N/10 
alkali till the color changes to a yellow which fairly matches 
the indicator; this represents the free HC1. To this mixture 
add a few drops of phenolphthalein solution, and continue the 
titration until a permanent pink color is obtained. The N/10 
alkali used will represent the total acidity, combined HC1, and 
organic acids. The organic acids will not be present in gastric 
contents in the presence of any appreciable amount of free 
HC1, as they are derived almost entirely from fermentations 
which are inhibited by the hydrochloric acid. 

Experiments with Pancreatic Juice. 

Exp. 261. Proteolytic Action. — To 25 c.c. of a 1% solution 
of Na2C03 add a few drops of the pancreatic extract. Place 
some pieces of fibrin in this liquid, and keep in the water bath 
at 40 C. till the fibrin has disappeared (one or two hours prob- 
ably). Observe the digestion from time to time. Note that 
the fibrin does not swell and dissolve as in gastric digestion, but 
that it is eaten away from the edges. 

Filter. What is the precipitate? Carefully neutralize the 
filtrate with 0.2% HC1. Another precipitate may appear. 
What is this? 

Again filter, if necessary, and test the filtrate for proteoses 
and peptones as directed under gastric digestion. 

Exp. 262. Amylolytic Action. — To some starch paste in a 
test-tube add a drop or two of the pancreatic extract and place 
in the water bath at 40 C. After a few minutes test for sugar 
and report the result. 

Exp. 263. The Piolytic {Fat-splitting) Action. — For the 
demonstration of this action use natural pancreatic juice, or 
finely divided fresh pancreas, or a recently prepared extract. 



422 EXPERIMENTS 

To some perfectly neutral olive oil, colored faintly blue 
with litmus, add half its volume of the pancreatic extract, 
shake thoroughly, and keep at 40 C. for twenty minutes. 
Record the result. Reserve for next experiment. 

Exp. 264. Emulsifying Action. — To 10 c.c. of a 0.2% solu- 
tion of Na 2 C0 3 add a few drops of the mixture used in Exp. 263. 
Shake thoroughly, and report the result. Referring to the 
earlier experiments on emulsification (see Fats), explain the 
efficacy of the pancreatic juice in emulsifying fats. 

Experiments with Bile. 

Exp. 265. Color. — Note the difference in color between 
human bile and ox bile. Explain. 

Exp. 266. Reaction. — Dilute some bile with four parts of 
water. Immerse a strip of red litmus paper, then remove and 
wash with water. Note the reaction. 

Exp. 267. Nucleo-albumin. — Dilute bile with twice its 
volume of water, filter if necessary, and add acetic acid. What 
is the precipitate? How distinguished from mucin? 

Exp. 268. Filter 267 and test the filtrate for proteins. 
Report the result. 

Exp. 269. Separation of Bile Salts. — Mix 20 c.c. of bile 
with animal charcoal to form a thick paste, and evaporate on the 
water bath to complete dryness. Pulverize the residue in a 
mortar, transfer to a flask, add 25 c.c. of absolute alcohol, and 
heat on the water bath for half an hour. Filter. To the fil- 
trate add ether till a permanent precipitate forms. Let the 
mixture stand for a day or two, and then filter off the crystalline 
deposit of bile salts. Save the filtrate which contains choles- 
terin. (Plate VII, Fig. 4, page 287.) 

Exp. 270. Bile- pigments. — (a) Gmelin's Test. — Take some 
bile in a wine-glass and underlay with yellow HNO3, in the 
manner described in testing saliva for albumin. Notice the 
play of colors, beginning with green and passing through blue, 



EXPERIMENTS WITH BILE 423 

violet, and red to yellow, at the junction of the two liquids. 
Explain. 

(b) Iodine Test. — Place 10 c.c. of dilute bile in a test-tube, 
and add slowly two or three cubic centimeters of dilute tincture 
of iodine, so that it forms an upper layer. A bright green ring 
forms at the line of contact. 

Exp. 271. Cholesterol. — Examine under the microscope the 
crystals obtained by the cautious evaporation of the alcohol- 
ether nitrate of Exp. 269. 

Concentrated H 2 S0 4 , containing a little iodine, gives with 
cholesterol a series of colors passing from violet to blue, then to 
green and finally red. 

Exp. 272. Action of Bile in Digestion. — (a) Take three 
test-tubes. In one mix 10 c.c. of bile and 2 c.c. of neutral olive 
oil; in the second, 10 c.c. of bile and 2 c.c. of rancid olive oil; 
in the third, 10 c.c. of water and 2 c.c. of neutral oil. Shake and 
place in a water bath at 40 C. for some time. Note the extent 
and the permanency of the emulsion in each case. 

(b) Into each of two funnels fit a filter-paper. Moisten one 
with water and the other with bile, and into each pour an equal 
volume of olive oil. Set aside for twelve hours (with a beaker 
under each funnel). Do you notice any difference in the rate 
of nitration? 

(c) Add drop by drop a solution of bile salts to (a) a solution 
of egg-albumin; (b) a solution of acid-albumin; (c) a solution 
obtained by digesting a bit of fibrin in gastric juice and filtering. 
Explain the results. 



APPENDIX. 
REAGENTS. 



It is desirable that all reagents be made with reference to the 
molecular weights of the substances employed. These may be 
from one to ten times the molecular weight per liter, while the 
solutions for practice are from one-tenth to one-fourth the 
molecular weight per liter. Salt solutions used as reagents are 
conveniently from five to ten per cent. ; that is, a molar concen- 
tration is selected bringing the strength within these limits. 

In the following list a few exceptions will be noted. 

Ammonia (dilute). — Strong ammonia one part, distilled 
water two parts. 

Ammonium Carbonate, 2M; 157 grams of commercial 
ammonium carbonate are dissolved by the aid of heat in about 
900 c.c. water. After this has become cold add 75 c.c. of con- 
centrated ammonium hydroxide, and make up volume to one 
liter. 

Ammonium Chloride, 4M, or about a twenty per cent, 
solution. 

Ammoniacal Cuprous Chloride may be made by dissolving 
copper oxide with metallic copper in dilute hydrochloric acid 
with the aid of heat. To the clear, cool, resulting solution add 
ammonia to marked alkaline reaction. 

Ammonium Molybdate Solution for Phosphates. — This may 
be made by dissolving twenty grams of ammonium molybdate in 
a mixture of 250 c.c. NH4OH and 250 c.c. of water. Then this 
solution is added to* 1000 c.c. of nitric acid making 1500 c.c. of 
reagent. In using this solution as a test for phosphates it is 

necessary to heat the mixture to about 6o° C. 

424 



REAGENTS 425 

If the reagent is prepared as follows it reacts without heating, 
is more sensitive than that produced by the first formula and is 
recommended as the better of the two. Dissolve 100 grams of 
molybdenum trioxide (molybdic acid) in 400 c.c. of dilute NH 4 OH 
(10%). Allow to cool and add all at once 1000 c.c. of dilute 
HN0 3 (HN0 3 three parts, H 2 two parts). The precipitate first 
formed is immediately redissolved and the product should be 
a perfectly clear, nearly colorless solution. 

Ammonium oxalate, M '4, 35.52 grams per liter. 

Ammoniacal Silver Solution. — Dissolve 10 grams of silver 
nitrate in 200 c.c. of water and add about 50 c.c. of strong 
ammonia, or an amount considerably in excess of that required 
to dissolve the precipitate first formed. 

Ammonium Sulphide. — Saturate 300 c.c. of strong ammonia 
with hydrogen sulphide gas. Then add an equal volume of 
strong ammonia and sufficient water to make 1000 c.c. In this 
solution dissolve one or two grams of sulphur, giving the yellow 
or ammonium sulphide (polysulphide) . 

Barium Chloride, BaCl 2 .2 H 2 0, M/2, or 122.16 grams per liter. 

Barfoed's Reagent. — Dissolve one part of copper acetate 
in fifteen parts of water; to each 200 c.c. of this solution add 
5 c.c. of acetic acid containing thirty-eight per cent, of glacial 
acetic acid. 

Benedicts Solution has the following composition: 

Gm. or c.c. 

Copper sulphate (pure crystallized) 17.3 

Sodium or potassium citrate 1 73 . o 

Sodium carbonate (crystallized) 200 . o 

or one-half the weight of the anhydrous salt 
Distilled water to make 1000 . o 

The citrate and carbonate are dissolved together (with the aid 
of heat) in about 700 c.c. of water. The mixture is then poured 
(through a filter if necessary) into a larger beaker or casserole. 
The copper sulphate (which should be dissolved separately in 




426 APPENDIX 

about ioo c.c. of water) is then poured slowly into the first 
solution with constant stirring. The mixture is then cooled and 
diluted to one liter.* 

Benzidine Solution. — Saturated solution of benzidine in 
glacial acetic acid with an equal volume of peroxide of hydrogen 
solution. The two solutions are to be mixed when used as a test 
for blood. 

The following method of making the benzidine solution is 
suggested by Hawk's Physiological Chemistry: 4.33 c.c. of glacial 
acetic acid is warmed in a small Erlenmeyer flask to about 50 C, 
a half gram of benzidine added, and the mixture heated eight 
or ten minutes at 50 C. and then the solution diluted with 19 c.c. 
of distilled water. If kept in a dark place it is fairly permanent. 

Congo Red. — Two per cent, aqueous solution. 

CuS0 4 Solution. — One per cent, for Biuret test. 

Dimethyl-amino-azobenzene. — 0.5 per cent, alcoholic solution. 

Esbach's Reagent. — Picric acid ten grams, and citric acid 
20 grams dissolved in sufficient water to make one liter of solution. 

Fehling's Solution. — The Fehling's solution recommended 
for experiments in this book is one-half the strength frequently 
employed, and is prepared in separate solutions as follows: 
Dissolve 34.639 grams of pure crystallized copper sulphate in 
water, and make solution up to one liter. This constitutes the 
first part of the reagent. The second part may be made by 
dissolving 173 grams of Rochelle salts and 52.7 grams of caustic 
soda (NaOH) in water and making up to one liter. When pre- 
pared in this way 10 c.c. of each of these solutions mixed to- 
gether will be reduced by 0.05 gram of glucose. 

Ferric Chloride. — 2.5 per cent, solution acidified with HC1. 

Goulard's Extract is a solution of lead subacetate, q.v. 

Gram's Solution. — See iodine solution. 

Gunzburg's Reagent. — Phloroglucin, 2 grams; vanillin, 1 
gram; alcohol, 100 c.c. 

* Jour. Amer. Med. Assoc, Oct. 7, 191 1, p. 1193. 



REAGENTS 427 

Hopkins-Cole Reagent, glyoxylic acid, CHO.COOH.H 2 0, is 

prepared by saturating a liter of water with oxalic acid, adding 
sixty grams of sodium amalgam and allowing to stand until 
reduction is complete or until hydrogen ceases to be evolved. 
For use this solution should be filtered and diluted with two or 
three volumes of water. 

Hydrochloric Acid (dilute). — Hydrochloric acid, strong, 
(sp. gr. 1.20) one part; distilled water, two parts. 

Hypobromite Solution for Urea. — Consists of a mixture of 
equal parts of the following solutions kept separately and mixed 
for use: 

Bromine Solution for Urea. — 125 grams KBr and 125 grams 
Br to one liter water. 

NaOH Solution for Urea. — A 40 per cent, solution, or a ten 
molar solution. 

Iodine Solution. — 10 grams iodine, 20 grams KI, made up 
with water to one liter. 

Iodine Tincture. — See tincture. 

Invertase. — Mix 500 gms. of " beer yeast," 200 c.c. of water 
and 10 gms. of sugar, allow to stand one hour. Add 50 c.c. of 
60% alcohol and a little thymol. Filter, press or allow to dry, 
put the nearly dry mass in a flask, add twenty gms. of sugar and 
shake till solution is effected. Keep in ice chest. 

If "beer yeast" is not available a solution of invertase, rather 
less satisfactory than the above, can be made as follows: Take 
one dozen compressed yeast cakes, grind with sand and mix 
with 500 c.c. of water, and a little chloroform as preservative. 
Allow to stand twelve hours and filter. 

Iodine Solution. — 

LugoVs solution is iodine five grams, potassium iodide ten 
grams, and sufficient distilled water to make one hundred grams. 
(U. S. P.) 

Gram's solution: Iodine one gram, potassium iodide two 
grams, and sufficient distilled water to make two hundred grams. 



428 APPENDIX. 

Lead Subacetate, or basic acetate of lead. The U. S. P. 
method of preparation is as follows: lead acetate 180 grams, lead 
oxide no grams, distilled water to make iooo grams. Rub lead 
oxide to a paste with ioo c.c. of water, dissolve lead acetate in 
700 c.c. of boiling distilled water; add slowly with constant 
stirring to lead oxide and boil the mixture for half an hour. 
Cool and filter and make up to 1000 c.c. with water free from 
carbon dioxide. 

Leucin. — See under Cystin, page 432. 

Lipase. — From castor bean (see page 399). Remove the 
shells from ten grams of fresh beans, break them up as fine as 
possible and allow to stand overnight in a loosely stoppered test- 
tube full of alcohol ether mixture. Pour off; grind the beans to 
a powder in a small mortar, transfer to a test-tube and let stand 
under ether overnight. Filter with suction and wash two or 
three times with small amounts of the alcohol ether mixture. 

Lipase. — From pancreas. Take a pig's pancreas, remove 
all fat, grind and allow to stand overnight. Then add four 
times its weight of 25% alcohol and allow to stand three days. 
Syphon off clear fluid and neutralize with sodium carbonate. 
The solution will contain a fat-splitting enzyme. 

Lugol's Solution. — See Iodine. 

Magnesia Mixture. — 125 grams of ammonium chloride, 
125 grams of magnesium sulphate, dissolved in sufficient water 
to make one liter of solution, then add 125 c.c. of strong am- 
monia water. 

Manners Reagent. — 10 grams potassium iodide, 5 grams 
cadmium iodide, 100 c.c. water. 

Mercuric Chloride Solution. — Five per cent. HgCl 2 in dis- 
tilled water. 

Millon's Reagent. — To one part of mercury add two parts 
nitric acid of specific gravity 1.4, and heat on the water bath 
till the mercury is dissolved. Dilute with two volumes of water. 
Let the precipitate settle, and decant the clear fluid. 



REAGENTS 429 

Molisch's Reagent for Carbohydrates. — Fifteen per cent, 
solution of a-naphthol in alcohol. 

Nessler's Solution. — An alkaline solution of potassio-mercuric 
iodide, made as follows: Dissolve 35 grams of potassium iodide in 
about 200 c.c. of water. Dissolve 17 grams of mercuric chloride 
in 300 c.c. of hot water. Add the potassium iodide to the mer- 
curic chloride, until the precipitate at first formed is nearly all 
redissolved. If the precipitate should entirely dissolve, add a few 
cubic centimeters of a saturated solution of mercuric chloride, 
until a slight permanent precipitate is obtained. After the 
mixture is cold, make up to one liter with a twenty per cent, 
solution of caustic potash. Allow to settle and use the clear 
solution. 

Nitric Acid (dilute). — Strong HN0 3 (sp. gr., 1.42) one part, 
and water three parts. 

Pancreatic Extract. — Obtain a fresh pancreas and soak in 
four times its weight of 25% alcohol for two or three days. 
Filter and make the solution neutral or very slightly alkaline 
with sodium carbonate. This solution will contain the fat- 
splitting enzyme. 

Phenoldisulphonic Acid. — Phenoldisulphonic acid, for esti- 
mation of nitrates in water analysis, may be prepared by heat- 
ing on a water bath for several hours a mixture of 555 grams of 
concentrated sulphuric acid and 45 grams of pure carbolic-acid 
crystals. 

Phenyl-hydrazine Solution. — One gram phenyl-hydrazine 
hydrochloride and two grams sodium acetate dissolved in 10 c.c. 
water. 

Picric-acid Solution (Esbach's Reagent). — Picric acid, ten 
grams; citric acid, twenty grams; dissolved in sufficient water to 
make one liter. 

Potassium Ferrocyanide Solution. — K4Fe(CN) 6 , one-fourth 
molar solution (9.2%). 

SchifFs Reagent. — Into 50 c.c. of a 2 per cent, solution of 



430 APPENDIX 

Fuchsine or Rosaniline pass S0 2 gas until the solution is colorless. 
Then dilute with an equal volume of water and keep in small full 
bottles in a dark place. 

Silver-nitrate Solution. — Drop solution, i : 8, used as a 
qualitative test for chlorine in urine. 

Quantitative Solution for Chlorine Titration in Urine. — 29.075 
grams silver nitrate, made up to one liter with water. 1 c.c. of 
this solution corresponds to 0.01 gram sodium chloride or 0.00607 
gram chlorine, or a N/10 silver nitrate solution may be used, one 
c.c. of which will be equivalent to 0.00355 gram of chlorine. 

Starch Paste (thin). — Rub about one-half gram of starch to 
a thin paste with cold water. Add sufficient boiling water to 
dissolve, then dilute to 100 or 150 c.c. 

Sulphuric Acid (dilute). — Twenty per cent, strong H 2 S0 4 in 
distilled water. 

Tincture Iodine for Bile Test. — Dilute the U. S. P. tincture 
with alcohol until just transparent in test-tube. 

Tollen's Reagent. — Make a 10 per cent, solution of AgN0 3 in 
dilute ammonia and just before using mix an equal volume of 
this solution with a 10% solution of NaOH. 

Tropseolin 00. — Saturated alcoholic solution. 

Uffelmann's Reagent. — Mix 10 c.c. of a four per cent, solution 
of carbolic acid with 20 c.c. of water, and add a drop or two of 
ferric chloride. 

PREPARATIONS. 

Creatin may be most conveniently prepared from a strong 
solution of Liebig's extract. Dissolve the extract in twenty 
parts of water, add basic lead acetate drop by drop to avoid more 
than a slight excess, then remove excess of lead; concentrate to 
a syrup over a water bath and allow to stand in a cool place, 
when creatin crystals will separate out. Two or three days' 
time may be required before the crystals are obtained. They 
may be washed with 88% alcohol and purified by recrystalliza- 



PREPARATIONS 431 

tion from water. Hypoxanthin and sarcolactic acid may be 
obtained from the mother liquor.* 

Creatinin may be prepared from creatin by boiling for ten or 
fifteen minutes with very dilute sulphuric acid. Neutralize the 
acid with BaCOs, filter, evaporate to dryness on a water bath, 
and extract the creatinin with alcohol. Upon evaporation the 
creatinin is obtained in the form of crystals. 

Cystin. — 1. Clean 200 grams of hair by washing with dilute 
HC1 and then with ether. Boil the clean hair with 600 c.c. of con- 
centrated HC1 (specific gravity, 1.19) for four hours (in a three- 
liter flask with condenser) on a sand-bath in hood. Then let cool. 

2. Add concentrated NaOH solution (750 c.c. H 2 0, 500 
grams NaOH) till the reaction is only faintly acid. 

3. Add to the solution, which has begun to boil on neu- 
tralization, plenty of animal charcoal, and boil three-quarters 
of an hour. 

4. Filter hot, being careful to moisten filter and funnel with 
hot water to prevent funnel from cracking. 

5. The filtrate should be faintly yellow. On cooling, a 
crystalline precipitate forms, mainly cystin, with some tyrosin 
and leucin. If this is not the case, or if the precipitate is slight, 
the solution must be concentrated. Save the filtrate, which with 
the filtrate from 6 is to be worked up later for tyrosin and leucin. 

6. After standing overnight filter off the precipitate. 

7. Dissolve this precipitate in 350 c.c. of hot 10 per cent. 
NH4OH (hood) and let cool. Then continue the cooling with 
finely chopped ice or with snow. Filter off any tyrosin that 
may have precipitated, and combine it with the filtrate of 6. 

8. Add glacial acetic acid, being careful not to acidify. The 
precipitate is a mixture of tyrosin and cystin. Filter. 

9. Make filtrate from 8 quite acid with glacial acetic acid. 
The precipitate is almost pure cystin. Let stand twenty-four 
hours. Then filter, and wash with H 2 and alcohol. 

* Lea's Chemical Basis of the Animal Body. 




432 APPENDIX 

10. Recrystallize by redissolving in as little hot 10 per cent, 
ammonia as is necessary to effect solution, cooling and precipitat- 
ing with glacial acetic acid. 

The preparations should be pure and contain no tyrosin, 
for which test may be made with Millon's reagent. 

Reactions. — Put a trace of cystin into a test-tube with some 
dilute NaOH and a little lead acetate. Boil. H 2 S is formed 
because S is split off. 

Tyrosin. — i. Concentrate the neutralized filtrate of 6 of 
cystin preparation till, on cooling, tyrosin crystallizes out. 

2. Filter, and save filtrate for the preparation of leucin. 

3. Dissolve the tyrosin crystals in very little hot water. 

4. Add amyl alcohol till a heavy precipitate forms. 

5. Filter precipitate. 

6. Redissolve in very little hot water, and let crystallize out 
by cooling. 

Examine crystals under the microscope. 
Test with Millon's reagent. 

Leucin. — 1 . Take the filtrate of 2 in the preparation of 
tyrosin, and evaporate to dryness on the water bath. 

2. Extract with alcohol. 

3. On standing, the leucin crystallizes out of the alcoholic 
extract as it evaporates. 

4. Filter, and dry the crystals. 
Examine under the microscope. 

Gelatin. — Take about 10 grams of bone, preferably small 
pieces of the shaft of a long bone, clean carefully, and allow to 
stand for a few days in 60 c.c. of dilute HC1 (1/20). The dilute 
acid dissolves the inorganic portion of the bone, leaving the 
collagen. Note the effervescence due to the presence of carbon- 
ates. The acid solution is poured off and kept for further 
investigation. The remains of the bone are allowed to stand 
overnight in a dilute solution (1/10) of Na 2 C0 3 , and then boiled 
in 100 c.c. of water for an hour or two. The collagen undergoes 



PREPARATIONS 433 

hydrolysis and is converted into gelatin, which dissolves. A core 
of bone untouched by the acid usually remains. Evaporate the 
solution to 25 c.c. bulk and allow to cool. A firm jelly is formed 
if the solution is sufficiently concentrated. If the solution 
gelatinizes, add an equal bulk of water and heat anew. If the 
solution thus obtained is sufficient in quantity it may be used 
for experiments 208 and 209. 

Gelatin may also be prepared from tendons which consist 
almost wholly of white fibers. Collagen is the substance of 
which white fibers are made up. 

Glycogen (C 6 Hio0 5 )n. — Use a liver taken from an animal 
just killed, or, if the season permits, oysters just removed from 
the shell. Cut an oyster, as rapidly as possible, into small 
pieces, and throw it into four times its weight of boiling water, 
slightly acidulated with acetic acid. After boiling the first por- 
tion for a short time, remove the pieces, grind in a mortar with 
some sand, return to the water, and continue the boiling for sev- 
eral minutes. Filter while hot. The opalescent solution thus 
obtained is an aqueous solution of glycogen and other substances. 

If a purer solution is desired, continue as follows : Add to the 
filtrate alternately a few drops of hydrochloric acid and potassio- 
mercuric iodide, until a precipitate of protein ceases to form. 
This may be determined more conveniently by filtering off a 
small portion of the liquid from time to time, and adding to the 
clear filtrate the hydrochloric acid and potassiomercuric iodide. 
When the precipitation of the proteins is complete, filter, and to 
the milky filtrate add double its volume of alcohol; the glycogen 
will precipitate as a white powder. Filter this off, wash with 
sixty-six per cent, alcohol (one part of water to two of alcohol), 
and dissolve in water. 

Mucin Solution. — Cut a portion of a navel-cord into small 
pieces. Shake in a flask with water, changing the water several 
times. This removes salts and albumin. Extract for twenty- 
four hours with lime-water or baryta- water in a corked flask. 



434 APPENDIX 

Filter. To filtrate add acetic acid, which precipitates the mucin. 
Let settle, filter, and wash with water. 

Mucin may also be prepared from the saliva by precipitation 
with acetic acid. 

Potassium Cyanate (KCNO). — Melt in an iron ladle, of at 
least 50 c.c. capacity, five grams of commercial potassium cyanide, 
and stir in gradually twenty grams of litharge. When the entire 
amount has been added, pour the mass out upon an iron plate, 
and allow to cool. Separate as far as possible the reduced lead 
from the potassium cyanate that has been formed, powder the 
latter, and dissolve in 25 c.c. of cold water. Filter if necessary 
and purify by repeated crystallization. 

Tyrosin. — See paragraph under Cystin, page 432. 

Urea, Synthesis of. — Add to a filtered solution of KCNO 
a cold saturated solution of ammonium sulphate, containing 
at least six grams of (NH^SCV Heat the mixture slowly on a 
water bath at a temperature of 6o° C, and maintain at that 
point for one hour. By this process ammonium cyanate is 
formed and then changed to urea, which may be obtained in an 
impure state by evaporating the solution to dryness on a water 
bath, and extracting the residue with hot, strong alcohol. The 
urea will crystallize from the alcohol as it cools. 

Vegetable Globulin : e.g. Edestin. Extract about one ounce 
of crushed hemp seed with water containing about 5% sodium 
chloride. This extraction should take from one-half hour to one 
hour at a temperature of about 6o° C. Filter while hot. Upon 
cooling, a portion of the globulin (edestin) will probably separate 
out. Use the clear separated fluid for the general protein 
reactions and precipitates. Boil the cloudy portion until the 
precipitated globulin has dissolved. Then set aside for twenty- 
four hours that the edestin may crystallize slowly, when hexag- 
onal plates should be obtained. Examine by the microscope. 
(See Plate VII, Fig. 1, page 287.) 



INDEX 



Absolute temperature, 13 
Acetaldehyde, 208 
Acetamide, 235 

preparation (Exp. 123), 393 
Acetanilide, preparation of, 249 

test for, 229 
Acetates, 100 
Acetic acid, 217 

(N/10) factor, 151 
test for (acetates), 100 
volumetric determination of, 15 

anhydride, 218 

ether, 215 
Acetone, 210 

bodies, 224 

chloroform, 176 

exp. with, 387 

in blood, 210 

in saliva, 300 

determination of, 313 

in urine, 350 

Legal's test for, 350 

preparation of (Exp. 90), 387 
Acetylene, 202 

preparation of (Exp. 67), 382 
Acetyl chloride, 218 

salicylic acid, 250 

urea, 239 
Achroodextrin, 263 
Acid (defined), 4 

albumin, 276 

albuminate, 276 

ammonium urate, 355 

groups, 93 

lactates in urine, 355 

metaprotein, 284 

preparation of (Exp. 224), 410 

phosphates in urine, 355 

potassium oxalate, 221 

protein, 275 

salts, 4 

urates (ammonium and sodium), 
Acidimetry, 149 
Acids of group I, tests for, 93 

of group II, tests for, 95 

of group III, tests for, 98 

of group IV, tests for, 100 



Acids, reactions of, 91 
Acoin, 173 
Acrylic acid, 219 

series, 219 
Acrylic aldehyde, 219 
Activators, 258 
Addition products, 199 
Adenin, 241 

Adjacent hydrocarbons, 245 
Adnephrine, 174 
Adrenalin, 174 
1 chloride, 174 

Adrenol, 174 
Aich's metal, 114 
Alabaster, 71 
Albumin in saliva, 298 

test for (Heller's), 314 

in urine, detection of, 343 
Esbach's test, 345 
heat test, 344 
nitric acid test, 344 
Albuminoids, 273, 277 
Albuminoscope, 344 
Albumins, 272, 275 

tests for, 407 
Albumose (Exp. 225), 411 
Albumoses, 285 
Alcohol, 206 

amyl, 207 

butyl, 207 

ethyl, 207 

grain, 207 

methyl, 207 

propyl, 207 

separation of water from (Exp. 76), 

384 
Alcoholates, 205 

Alcoholic fermentation in milk, 284 
Alcohols, 205 

atomicity of, 206 

classification of, 206 

exp. with, 384 
355 oxidation of, 208 

Aldehyde, 208 

acetic, 208 

acrylic, 219 

benzoic, 250 

formic, 179, 208 

435 



43 6 



INDEX 



Aldehydes, test for (Exp. 83, 84, 85), 

386 
Aldose, 259 

Algaroth, powder of, 39 
Aliphatic hydrocarbons, 198 
Alkali (denned), 4 

albumin, 276 

albuminate, 276 

aluminates, 57 

metaprotein, 285 

proteins, 275 
Alkalimetry, 149 
Alkaline earths, 69 

exp. with, 375 
Alkaline metals, 78 

exp. with, 376 
Alkyl (term defined), note, 205 
Alkylated ureas, 239 
Alloxan, 241 
Alloys (denned), 114 

analysis of, 166 

dental, composition of, 125 

eutectic, 117 

list of, 114, 115 

microscopical examination of, 117 

of bismuth, 30 

of cadmium, 31 

of copper, 26 

of lead, 23 

of mercury, 21 

of silver, 19 

preparation of, 115 
Allylene, 202 
Alum, 56 
Aluminates, 56 
Aluminium, 55 

alloys, 56 

amalgam, 121 

bronze, 56, 114 

cobalt test for. 59 

compounds, 56 

properties of, 56 

reactions of, 56 

solder for, 130, 131 

sulphate, 56 
Alypin, 174 

andKI (PL IV, Fig. 6), 172 

microchemical test, 174 

nitrate, 174 
Amalgam (defined), 114 

alloy, 114 

effect of metals in, 123 
Amalgamation process (silver ore), 18 
Amalgams, excess of mercury in, 125, 
126 



Amalgams, methods of making, 119 

properties of, 119 

tests for, 126 
Amandin, 273 

Ames, Dr., on use of beryllium, 140 
Ames' oxyphosphate of copper, 138 
Amides, 235 
Amines, 233 
Amino acetic acid, 226 

acids, 225 

benzene, 248 

preparation of (Exp. 138), 396 

ethyl-sulphonic acid, 232 

formic acid, 225 
Amino glutaric acid, 227 

isobutyl-acetic acid, 226 

phenol, 249 

succinic acid, 227 

valeric acid, 226 
Ammelid, 238 
Ammonia, 85 

alum, 56 

determination in urine, 335 

dilute, 424 

process (Na^CC^), 82 

water, 85 
Ammoniacal cuprous chloride, 424 
Ammoniacal silver nitrate solution, 334, 

425. 
Ammoniated mercury, 28 
Ammonium, 85 

acetate, 86 

acid urate (PI. IX, Fig. 1), 353 

amalgam, 121 

bifluoride, 174 

carbamate, 226 

carbonate, 85 
solution of, 424 

chloride, 86 

(PI. VIII, Fig. 1), 316 
solution of, 424 

compounds of, 85 

cyanate (Exp. 126), 393 

hydroxide of, 85 

magnesium phosphate, 75 

magnesium phosphate (microchemi- 
cal formation), 171 

molybdate solution, 424 

nitrate, 86 

oxalate solution of, 425 

phosphate, 87 

picrate (Exp. 148), 397 

platinic chloride, 46, 47 
(PI. Ill, Fig. 1), 171 

reactions of, 87 



INDEX 



437 



Ammonium, salts, 86, 87 


Argols, 80 


in saliva, 301 


Argyrol, 175 


determination of, 310 


Arington's alloy, 125 


sodium phosphate, 87 


Aristol, 175 


sulphate, 86 


Aromatic acids, 249 


sublimed (PI. I, Fig. 4), 106 


hydrocarbons, 244 


sulphide, 86 


experiments, 395 


solution, 425 


Arrowroot (PI. VI, Fig. 6), 262 


Amoss, Dr. H. L., phenolphthalein, Ref., 


Arsenic, antidote for, 33 


300 


compounds, 38 


Amphoteric reaction of milk. 281 


in urine, determination of, 352 


Amyl acetate, 215 


reactions for, 33 


alcohol, 207 


special tests for, 34 to 38 inc. 


butyrate, 215 


stains, tests for, 36 


nitrite, 215 


trioxide, 32 


valeriate, 219 


(PI. I, Fig. 2), 106 


Amylolytic enzymes in saliva, 313 


volumetric determination, 157 


Amylopsin, 321 


Arsenical pyrites, 32 


Anabolism (defined), 361 


Arsenious acid, 32 


Anaestheaine, 175 


compounds, 32 


Analytical groups, 17 


hydride, 33 


Analysis by precipitation, 158 


Arseno benzol, 249 


in dry way, 102 


Artificial enamel, 138 


of groups {see Groups) 


Ascher's artificial enamel, 139 


of saliva, 304 


Asbestos, 74 


Anesthol, 175 


Ash in saliva, 315 


Aniline, 248 


Asparaginic acid, 227 


oil, 248 


Asparagus, succinic acid in, 221 


preparation of (Exp. 138), 396 


Aspartic acid, 227 


Annealing of alloys, 116 


Aspirin, 250 


gold, 43 


Asymmetric carbon, 223 


platinum, 117 


Atomicity (defined), 4 


Antialbumid, 276 


of alcohols, 206 


Antialbuminate, 276 


Atoms (defined), 2 


Antialbumose, 276 


Atropin and test, 175 


Antifebrin, preparation of, 249 


Aurum, 42 


test for, 229 


Available oxygen in H2O2, 155 


Antimonite, 38 


Avogadro's law, 14 


Antimony, 38 




alloys, 39 


B. 


butter of, 39 


Babbitt's metal, 128 


in dental alloys, 124 


potash, 81 


oxychloride, 39 


Balanced diet, 362 


potassium tartrate, 225 


Banca tin, 40 


properties of, 38 


Barfoed's reagent, 425 


reactions of, 39 


solution, 261 


stains, test for, 36 


test (Exp. 171), 401 


Antimonyl salts, 39 


Barium, 70 


Antiseptic tablets, 28 


chloride, solution of, 425 


Apatite, 72 


hydroxide, 70 


Apple essence, 219 


peroxide, 70, 180 


Aqua ammonia, 85 


reactions of, 70 


regia, 48 


salts, flame test, 71 


Arabinose, 259 


sulphate, 70 


Argentum, 18 


Baryta-water, 70 



43§ 



INDEX 



Base (defined), 4 

metal, 16 
Basic acetate of lead, 23 

salts, 5 
Basicity of acids, 216 
Bastard metals, 16 
Battery (cut), 113 
Bauxite, 55 
Bayberry wax, 219 
Bead test with microcosmic salt, 109 
Bell-metal, 114 
Benedict's solution, 425 

test for sugar, 348 
also (Exp. 170), 401 
Benzaldehyde, 250 
Benzene, 244 

preparation of (Exp. 135), 395 
Benzidine, 248 

solution, 426 

test for blood (Exp. 238), 414 
Benzine, 200 
Benzoated lard, 250 
Benzoates, 250 
Benzoic acid, 249 

experiments with, 397 

sublimed (PI. V, Fig. 5), 204 
Benzol, 244 

Benzosulphinidum, 184 
Benzoyl glycocoll, 251 
Beryl, 139 
Beryllium, 69 

test for in cement, 139 
Berzelius' test for arsenic, 36 
Beta eucaine, 178 

and PtCU (PI- HI, Fig. 2), 171 
Beta oxybutyric acid, 224 

in urine, 351 
Bile, 322 

experiments with, 42 1 

pigments, tests for (Exp. 270), 422 

salts, preparation of (Exp. 269), 
422 
Bilirubin, 322 
Biliverdin, 322 
Binary amalgams, 121 
Biogen, 180 
Bismuth, 30 

alloys, 30 

compounds, 30 

in dental alloys, 124 

ochre, 30 

oxysalts of, 30 

properties of, 30 

reactions of, 31 

sodium stannite test for, 48 



Biuret, 238 

formation of (Exp. 127), 394 

reaction (Exp. 189), 406 
Black and Sanger, Gutzerits' test, 37 
Black ash, 82 
Black, Dr., annealing of alloys, 116 

gold in alloys.. 124 
Black's dynamometer, Ref., 120 
Black wash, 22 
Blast furnace, action of, 53 
Blaud's pills, 54 
Block tin, 40 
Blood, 286 

benzidene test for, 414 

chicken (PL VII, Fig. 6), 287 

corpuscles, 287 
number of, 288 

dog (PI. VII, Fig. 5), 287 

experiments with, 412 

fish (PI. VII, Fig. 6), 287 

frog (PL VII Fig. 6), 287 

guaiacum test for, 413 

horse (PL VII, Fig. 5), 287 

human (PL VII, Fig. 5), 287 

plasma, 286 

serum, 286 

specific gravity of (Exp. 236), 413 

spectroscopical examination of, 412 

urinary sediment; 357 
Bloor's nephelometer, 296 
Blow pipe tests, 107, 108 
Blue stone and blue vitriol, 27 
Boas' reagent and test for HC1 (Exp. 

255c), 419 
Bond (explained), 3 
Bone, 279 

earth, 279 

marrow, 279 
Borates, 99 
Borax, 176 

bead, method of making, 61 

bead test, 109 
Boric acid, tests for, 99 
Brass, 114 

solder for, 131 
Brick dust deposit, 241 
Britannia metal, 114 
Bromoform, 203 
Bromides, 95 

separation from iodides, 97 
Bronze, 114 
Buckley, Dr. J. P., Europhen. Ref., 

179 
Buckley's phenol compound, 184 
Butane, 197, 201 



INDEX 



439 



Butter crystals (PI. VII, Fig. 3), 287 

fat, 215 

of antimony, 39 
Butylene, 202 

diamine, 234 
Butyric acid, 218 
Butyrin, 215 
Bynin, 277 



Cacodyl, 204 
Cadaverin, 234 
Cadmium, 31 

alloys of, 31 

amalgam, 123 

in dental alloys, 124 

oxalate (microchemical), 171 

oxalate (PL II, Fig. 2), 170 

reactions of, 32 
Caffein, 241 
Calamine, 64 
Calcium, 71 

acid lactate (PL VIII, Fig. 4), 316 

in saliva, 312 

in teeth and tartar, 192 

lactate, 224 

(PL VIII, Fig. 3), 316 

metabolism of, 364 

oxalate (microchemical), 171 
(PL II, Fig. 1), 170 
in urine, 356 

phosphate in tartar, 191 

reactions of, 73 

sarcolactate, 224 

volumetric determination of, 162 
Calc-spar, 71 
Calomel, 21 

Calorie (defined), 362 • 
Calverite, 42 
Camphors, 265 
Cane sugar, 262 
Carat (defined), 43 

rules for changing, 44 
Carbamic acid, 225 
Carbamide (Urea), 237 
Carbimide, 230 
Carbinol, 206 

Carbocyclic compounds, 254 
Carbohydrates, 194 

classification, 259 

metabolism of, 363 

Molisch's test for, 400 
Carbolic acid, 176, 183 
Carbonates, 93 

in saliva, 300 



Carbonates, titration of, 152 
Carbon dioxide in saliva, 293, 296 

experiments, 380 
Carbonic acid, 220 

in teeth and tartar, 192 
Carbon monoxide hemoglobin (Exp. 

2 35 d), 288 

Carbon, test for in organic compounds, 
194 

tetrachloride, 203 
Carboxyl, 216 
Carbylamine, 233 
Carnallite, 78 
Carnin, 289 
"C. A. S." alloy, 125 
Casein, 283 
Caseinogen, 283 
Cassiterite, 40 
Cast iron, 53 
Casts, fibrinous, 357 

renal, 357 
Catabolism (defined), 361 
Catalase (defined), 258 
Caustic soda, 81 
Cellulose, 264 
Cement, composition of, 189 

dental, 135 

general tests for, 135, 136 
Centigrade thermometer, 12 

to Fahrenheit degrees, conversion of, 

13 
Centinormal solution, 146 
Cerussite, 22 
Chalcocite, 26 
Chalcopyrite, 26 
Chalk, 71 
Charles, law of, 13 
Chase's copper amalgam alloy, 125 

incisor alloy, 125 
Chemical affinity, 2 

equilibrium, 8 
Chemism, 2 
Chili saltpeter, 81, 83 
Chloral, 208 

alcoholate, 176 

hydrate, 176, 209 

test for, 176 and (Exp. 87, 88), 387 
Chlorates, 100 
Chlorethyl, 204 
Chloretone, 176 
Chlorides, determination of in saliva, 311 

in urine, 336 

metabolism of, 364 

tests for, 94, 96 
Chlorinated lime, determination of, 156 



44Q 



INDEX 



Chlorine in saliva, titration of, 160 

in teeth and tartar, 192 

in urine, titration, 161, 337 

titration, 159 
Chloro-chromic anhydride, 58 

test, 96 
Chloroform, 176, 203 

preparation of (Exp. 70), 383 

test for, 177 
Cholesterol, 323 

(Exp. 271), 423 

(PI. VII, Fig. 4), 287 

in saliva, 301 
Chromates, 98, 99 
Chrome alum, 56, 57 

iron ore, 57 

yellow, 23 
Chromic anhydride, 57 

oxide, 57 

salts, 57 
Chromite, 57 
Chromium, 57 

compounds, 57 

reactions of, 57 
Chromous salts, note, 57 
Chylous urine, 328 
Chymosin, 322 
Cinnabar, 20 
Citric acid, 222 
Classification of metals, 15 
Closed chain hydrocarbons, 244 
Closed tube test, 105 
Cloudy urine, causes of, 328 
Coagulated proteins, 275 
Coarse solder, 129 
Cobalt, 61 

borax bead, 61 

nitrite, 61 

reactions of, 61 

separation from nickel, 67 

test for aluminium, 59 
Cobaltite, 61 
Cocaine, 177 

and KMnCX (microchemical crystals), 

(PI. Ill, Fig. 4), 171 

and substitutes, differentiation of, 188 

test for, 177 

with tin chloride (PI. IV, Fig. 3), 172 
Coefficient of Haeser, 331 
Coefficients of expansion, 112 
Coin silver, 19, 114 
Collagen, 278 
Colloidal solution, 9 
Colloids, 10 



Colorimeter (cut), 295 

Coloring matter in urine, 341 

Color reactions for proteins, 405 

Colors of salts, 103 

Color test for amalgams, 126 

Colostrum, 284 

Common solder, 129 

Completed reactions, 5 

Complex ions (Exp. 122), 392 

Compound ethers, 211, 214 

Compounds (defined), 3 

Conductivity of metals, in 

Condy's fluid, 63 

Congo-red solution, 426 

Conjugated proteins, 274, 280 

Contraction test for amalgams, 126 

Cook, Dr. G. W., on mucin in saliva, 

Ref., 298 
Cook, Dr. R. H., on determination of 

uric acid, Ref., 334 
Cooking soda, 79 
Copper, 26 

alloys, 26 

amalgam, 122 

black oxide of, 27 

compounds of, 26 

glance, 26 

gravimetric determination of, 164 

in dental alloy, 124 

oxyphosphate (Ames'), 138 

properties of, 26 

pyrites, 26 

reactions of, 27 

sulphate, 27 

for Biuret test, 426 

red oxide of , 26 

volumetric determination of, 161 
Copperas, 54 • 
Cork in urine sediment (PI. IX, Fig. 6), 

353 
Corn starch (PL VI, Fig. 5), 262 
Corrosive sublimate, 28, 181 
Corrugated gold, 43 
Corundum, 55 

Cotton fibers (PI. IX, Fig. 6), 353 
Cotton seed oil, 219 
Cream of tartar, 80, 225 
Creatin, 289, 430 
Creatinin, 289, 431 
Creolin, 248 
Creosote, 177 

difference from carbolic acid, 177 
Cresol, 177, 248 
Cresylic acid, 248 
Crushing strength of amalgams, 127 



INDEX 



441 



Cryolite, 81 

process (Na2CC>3), 82 
Cryoscopy, 14 

Crystallization, experiments, 368 
Crystals, formation of, 169 

from saliva, 316 
Cuprammonium compounds, 27 
Cupric oxide, 27 
Cuprous oxide, 26 
Curd, 282 
Cyanamide, 235 
Cyanic acid, 230 

(iso), 230 
Cyanides, test for, 94 
Cyanogen, 228 
Cyanogen compounds, 228 

experiments, 391 
Cyanuric acid, 238 
Cyclic compounds, 254 
Cylinder oil, 200 
Cystin, 227 

(PL X, Fig. 6), 355 

in urine, 356 

preparation of, 431 
Cystoglobulin, 274 

D. " 
Dead burnt plaster, 72 
Decinormal factor, 145 

solutions (defined), 146 
Defibrinated blood, 286 
Degree of acidity explained, 282 
Dental alloys, composition of, 125 

cement, 135 

gold, 114 
Dentine, composition of, 189 
Derived albumins, 276 

proteins, 274, 284 
Deutero albumose (Exp. 224), 411 
Dextrin, 263 
Dextrose, 260 
Diabetic sugar, 260 
Diacetic acid, 224 

in urine, 351 
Dialyzer, 316 
Dialysis, 10 

(exp. n), 369 

of saliva, 316 
Diamines, 234 
Diastase, 262 
Dibasic acids, 220 
Dichlor-methane, 203 
Diet, "balanced," 362 
Dilute ammonia, 424 

hydrochloric acid, 427 



Dilute nitric acid, 429 

sulphuric acid, 430 
Dimethylamine, 234 
Dimethyl-amino-azo-benzene test for 
HC1 (Exp. 255), 419 

solution of, 426 
Dimethyl arsine, 204 

benzene, 245 

ketone, 210 

oxalate (Exp. no), 390 
Diphenylamine, 249 
Dioses, 262 
Disaccharides, 262 
Diureides, 239 
Dolomite, 74 
Donovan's solution, ^ 
Doremus-Hinds urea apparatus, 333 
Double-bonded hydrocarbons, 201 
Dualistic formulae, 3 ' 
Ductility of metals, in 
Dutch metal, 115 

Du Trey's synthetic porcelain, Ref., 140 
Dyad-mercury, compounds of, 28 

reaction, 29 
Dynamometer, Black's, 120 
Dysalbumose (Exp. 224), 411 

E. 

Earthy phosphates in urine, 337 
Edestin, 273 

preparation of, 434 

(PL VII, Fig. 1), 287 
Egg albumin, 275, 276 
Ektogan, 177 
Elastin, 278 
Electrons (defined), 2 
Electro-properties of metals, 113 
Elements (defined), 3 
Eleopten, 265 
Empirical formulae, 3 
Emulsification (Exp. 185), 404 
Enamel, artificial, 138 
Enamel, composition of, 189 
Endelman, Dr., on phenolphthalein, 

Ref., 183 
End point (defined), 145 
Enterokinase, 321 
Enzymes, 256 

experiments with, 398 

properties and classification, 257 
Epinephrine, 177 
Epithelium in urine, 356 
Epsom salt, 74 

Equations, method of balancing, 6 
Equilibrium (defined), 7, 9 



442 



INDEX 



Equivalent weights and measures, 12 

Erepase, 323 

Erepsin, 323 

Erythrodextrin, 263 

Esbach's reagent, note 345, 426 

Essence of checkerberry, 250 

Esters, 211, 214 

exp. with, 388 
Ethane, 200, 201 
Ether, preparation. of, 212, 213 

(also Exp. 93), 388 
Ethers, 211 
Ethyl acetate, 214 

alcohol, 207 
Ethylates, 205 
Ethyl benzene, 246 

bromide, 204 

butyrate, 215 

chloride, 178, 204 
Ethylene, 202 

-diamine, 234 

preparation of (Exp. 64), 382 
Ethyl ether, 212 

hydrazine, 236 
Ethylidene lactic acid, 222 
Ethyl mercaptan, 231 

nitrite, 214 

oxide, 212 

urea, 239 
Eucaine, 178 

and PtCL, (PI. Ill, Fig. 2), 171 

lactate, 178 
Eudrenin, 178 
Eugenol, 179 
Europhen, 179 
Eutectic alloys, 117 
Euzone, 180 

Evaporation, microchemical, 170 
Expansion of metals, 112 

test for amalgams, 126 
Extraction of metals from ore, 15 



False casts and mucin (PI. IX, Fig. 5), 

353 
Fahrenheit thermometer, 12 

to Centigrade degrees, conversion of, 

13 
Fat acid (PI. VII, Fig. 4), 287 

crystals (PI. VII, Fig. 3), 287 

in urine, 358 

of milk, 284 
Fats, 215, 265 

chemistry of, 265 

experiments with, 403 



Fats, metabolism of, 363 

saponification of, 267 
Fatty acids, 216 

preparation of (Exp. 183), 404 
Fatty casts, 358 
Fehling's solution 426 
Fehling's test for sugar (Exp. 167), 401 
Fellowship alloy, 125 
Fenwick, Dr. S., on KCNS in saliva, 

Ref., 302 
Ferments, 256 
Fermentation test for sugar (Exp. 172), 

349, 4oi 
Ferric alum, 56 

chloride, 54 
solution of, 426 

ferrocyanide, 55 

sulphate, 54 

sulphocyanate, 55 

ionization of (Exp. 16), 371 

thiocyanate, 55 
Ferricyanide, detection of, 97 
Ferris, Dr. H. C, methods of saliva 

analysis, Ref., 304 
Ferris ureometer, 308 
Ferrous carbonate, 54 

sulphate, 54 
Fibrin, 286 

ferment, 286 
Fibrinogen, 286, and (Exp. 241), 414 
Fibrinous casts, 357 
Filtration, microchemical, 170 
Fine solder, 129 
Fire damp, 200 
Flagg's submarine alloy, 125 
Flame test, 106, (note), 80 
Fleitmann's test, 35 
Fletcher's gold alloy, 125 
Fletcher's metallic cement, 30 
Fletcher melting apparatus, 116 
Flow of amalgam, 120 
Folin's ammonia test, 310 

new method for ammonia in urine, 335 
Fool's gold, 53 
Formaldehyde, 208 

method for ammonia in urine, 336 
Formaldehydurea, 354 

(PI. X, Fig. 5), 355 
Formalin, 179 

test for, 385, 386 
Formamide, 235 
Formanilide, 235 
Formic acid, 217 

ether, 212 
Formine, 179 



INDEX 



443 



Formol, 179 

Formose, 208 

Formula (denned) , 3 

Fowler's solution, 33 

Fractional distillation, 200 

French chalk, 74 

Freund & Topfer, test for acidity of 

urine, 330 
Frohde's reagent, 182 
Fruit sugar, 261 
Fulminic acid, 230 
Furfuraldehyde, 260 
Fusel oil, 207 
Fusible metals, 1 28 

G. 

Gad's experiment (Exp. 185), 404 

Galactose, 261 

Galena, 22 

Gallic acid, 251 

Gallotannic acid, 186 

Garnierite, 62 

Gasolene, 200 

Gastric contents, analysis of, 417 

titration for acidity (Exp. 260), 421 
Gastric digestion, 319 

lipase, 320 
Gay-Lussac, law of, 13 
Gelatine, 279 

experiment with, 409 

preparation of, 432 
German silver, 62, 115 
Glacial acetic acid, 217 
Glauber's salt, 84 
Gliadin, 277 
Globin, 273 
Globulins, 272, 276 

reactions of, 277 

tests for, 407, 408 

vegetable, 434 
Glonoin, spirit of, 182 
Glucinum, 69 
Gluconic acid, 260 
Glucosazone, 261 

(Fig. 1, PI. VI), 262 
Glucose, 260 

tests for, 261 (also Exp. 167, etc.) 
Glue, 279 
Glutamic acid, 227 
Glutelins, 277 

(denned), 273 
Glutenin, 277 

Glycerol (glycerine), 179, 215 
Glyceryl, 215 

butyrate, 215 



Glyceryl, oleate, 266 

palmitate, 266 

stearate, 266 
Glycin, 226 

Glycocholic acid in bile, 323 
Glycocoll, 226 

relation to urea, 323 
Glycogen, 263 

isolation of, 433 

in muscle, 290 

in saliva, 312 
Glycol, 220 
Gly collie acid, 222 
Gly co-proteins, 280 

(defined), 274 
Glyoxylic acid (Exp. 190), 406 
Gmelin's test for bile (Exp. 270), 422 
Gold, 42 

alloys, 43 

aluminium solder, 131 

amalgam, 122 

annealing of, 43 

carat, 43 

corrugated, 43 

gravimetric determination of, 165 

in dental alloys, 124 

melting-point of, 42 

non-cohesive, 43 

precipitation of, 45 

reactions of, 44 

scraps, recovery of, 141 

solders, 131, 132, 133 

solubility of, 42 . 

volumetric determination of, 157, 
1S8 
Goulard's extract (lead subacetate), 23 

preparation of, 426 
Grain alcohol, 207 
Gram's solution (iodine), 179 

strength of, 426 
Grape sugar, 260 
Graphic formulae, 3 

tellurium, 42 
Gravimetric determination, 163-167 
Gravity, specific, 13 
Green vitriol, 54 
Group I, analysis of, 24 
exp. with, 372 
outline of, 25 

II, analysis of, 47 
exp. with, 372 
outline of, 51 

III, analysis of, 58 
exp. with, 373 
outline of, 60 



444 



INDEX 



Group IV, analysis of, 66 
exp. with, 374 
outline of, 68 
V, analysis of, 75 
exp. with, 375 
outline of, 77 
reagents, 16 
Groups I- VI, metals of, 17 
III, IV and V analysis, 90 
phosphates present, 88 
Guaiacol, 246 

Guaiacum test for blood (Exp. 237), 413 
Guanin, 241 
Gun cotton, 264 
Gun metal, 115 
Gunzburg's reagent, 419, 426 

test (Exp. 255b), 419 
Gutta-percha, 179 
Gutzeit's test, 34 

Gutzeit's test (Sanger and Black), 37 
Gypsum, 71 

H. 

Halogens (organic), test for, 196 
Haloid derivatives of the paraffins, 203 
Hard solder, 129 
Harris' amalgam alloy, 125 
Head, Dr. Joseph, bifluoride of am- 
monia, Ref., 174 
Heavy spar, 70 
Helium, 70 
Hematite, brown, 53 
Hematite, red, 53 
Hematin, 288 
Hematopophyrin, 328 
Hemin, 289 

crystals, preparation of (Exp. 239), 414 
Hemialbumose, 276 
Hemipeptone, 276 
Hemochromogen, 287 
Hemoglobin, 288 

crystals, preparation of (Exp. 234) , 41 2 
Hemoglobins (defined), 274 
Heroin, 180 
Heteroalbumose, 411 
Heterocyclic compounds, 254 
Heteroxanthin, 241 
Hexoses, 260 
High-grade alloy, 125 
Hile, Dr. E. O., on Du Trey's porcelain, 

140 
Hippuric acid, 226, 251 

(PI. V, Fig. 4), 204 
Histones (defined), 273 
Hofmann's carbylamine reaction, 233 



Homocyclic compounds, 254 
Homologues, 197 
Hopkins-Cole reagent, 427 
reaction (Exp. 190), 406 
Hopkin's method for ammonia in urine, 

335 
Hopogan, 180 
Hordein, 277 
Horismascope, 344 
Horn silver, 18 
Howe, Dr. J. Morgan, KCNS in saliva. 

Ref., 303 
Howe, Dr. Percy R., calcium determi- 
nation, Ref., 162, 312 
Howe, Dr. Percy R., phosphates in 

saliva, 87 
Howe, Dr. Percy R., tartar deposits, 

190 
Hydrargyrum, 20 
Hydrazines, 235 
Hydraulic mining, 42 
Hydrocarbons, 196 

experiments with, 380 
Hydrochloric acid, vol. determination 
of, 151 

dilute, 427 

in stomach, 320 

test for free (Exp. 255), 419 
Hydrocyanic acid, 228 

preparation of (Exp. 115), 391 
Hydrogen dioxide (peroxide), 180 

factor for, 155 

preparation of, 371 

strength of, 155 

test for in organic compounds, 194 
Hydrolysis, defined, 4, 8 

experiments, 370 
Hydroquinol, 247 
Hydroxy acids, 222 

acetic acid, 222 

benzene (phenol), 183, 246 

propionic acid, 222 

succinic acid, 222 

toluene, 248 
Hypobromite solution for urea, 427 
Hypochlorite determination, 156 

test for, 96 

reaction with silver nitrate, 95 
Hypophosphites, test for, 97 
Hypoxanthin, 241 



I. 



Ignition tests, 104 
Imides, 234 
Imino group, 234 



INDEX 



445 



Indicators, 148 

Indol, 253 

Indoxyl (indican), 253 

in urine, 341 

-potassium sulphate, 253 
Inorganic matter in teeth and tartar, 

191 
Inosite, cqo 
Intestinal juice, 323 
Invertase, 427 

Iodides, separation from bromides, 97 
Iodine, N/10 solution of, 155 

determination, 156 

in ductless glands, 366 

(PI. I, Fig. 6), 106 

solution, 427 

test for bile pigment (Exp. 270), 423 

tincture for reagent, 427 
Iodoform, 204 

(PL V, Fig. 1), 204 

preparation of (Exp. 72), 383 
Ionization, 7 

(Exp. 16), 371 

(Exp. 122), 392 
Ions, 3 
Iridium, 46 
Iron, 53 

by hydrogen, 54 

compounds of, 54 

melting-point of, 54 

metabolism of, 365 

pyrites, 53 

reactions of, 54 and (Exp. 30, 31), 373 

reduction from ore, 53 
Iron scale, salts of, 225 
Isobenzonitril, 229 

test for chloral, 387 
Isobutyl carbinol, 207 
Isocyanic acid, 230 
Isocyclic compounds, 254 
Isomers, 197 
Isomerism, 197 

physical {see stereoisomerism) 
Isonitrils, 229 

K. 

Kalium, 78 

Kekule's benzene ring, 244 
Kephir grain, 284 
Kerargyrite, 18 
Keratins, 278 

experiments with, 408 
Kerosene, 200 
Ketones, 209 
Ketose, 259 



Kieserite, 74 

King's occidental alloy, 125 

Kingzett's method for hydrogen 

peroxide titration, 156 
Kirk, Dr. E. C, carbon dioxide in blood, 

Ref., 300 
Kjeldahl process of oxidation, 195 
Kumiss, 284 

L. 

Lacmoid, 148, 247 
Lactalbumin, 283 
Lactic axid, -?2 2 

in muscle, 290 

in tartar, 191 

optical activity of, 223 

test for (Exp. 114), 391 

test for (Exp. 257), 420 
Lactose, 262 

Lactosazone (PI. 6, Fig. 3), 262 
Lard crystals (PL VII, Fig. 3), 287 
Law of Avogadro, 14 

Charles, 13 

Gay-Lussac, 13 

partition, 9 
Lead, 22 

acetate, 23 

alloys, 23 

arsenate, 23 

black oxide of, 23 

compounds of, 23 

in urine, determination of, 352 

oxides, 23 

properties of, 22 

reactions of, 23, 24 

reduction from lead sulphide, 22 

solubility in water, 22 

subacetate, 23 

solution of, 428 
LeBlanc process (sodium carbonate), 

82 
Lecithin, 267 

in saliva, 301 
Lecitho-proteins (defined), 274 
Legal's test for acetone, 350 
Leptothrix, 318 
Leucin, 226 

(PL V, Fig. 2), 204 

in saliva, 301 

preparation of, 428 
Leucocytes, 288 
Levulose, 210, 261 
Ligno-cellulose, 264 
Limestone, 71 
Limonite, 53 



446 



INDEX 






Lipase, 322 

from castor bean (Exp. 159), 399 
preparation, 428 

from pancreas, 428 
Litharge, 23 
Lithium, 84 

salts and uric acid, 242 
Litmus, 148 
Liver of sulphur , 80 
Local anesthetics, 173 
Low's gold solder, 133 
Lugol's caustic iodine, 181 

iodine solution, 181, 428 
Lunar caustic, 20 
Lycopodium (PI. IX, Fig. 6), 353 

M. 
MacDonald, Dr. C. F., oxidases in 

saliva, 299 
Magnalium, 56 
Magnesia, light and heavy, 74 

mixture, 428 
Magnesite, 74 
Magnesium, 74 

acid lactate (PI. VIII, Fig. 4), 316 

alloys, 74 

amalgam, 122 

ammonium phosphate (PI. IV, Fig. 2), 
172 

carbonate, 74 

compounds, 74 

effect of, on metabolism, 365 

in teeth and tartar, 192 

lactate (PI. VIII, Fig. 3), 316 

oxide, 74 

phosphates, 75 

reactions of, 74 

sulphate, 74 

hydrate titration of, 152 
Mane, Dr. G., sodium chloride and 

toxicity, Ref., 185 
Malachite blue, and green, 26 
Malic acid, 222 

test for in vinegar (Exp. 113), 391 
Malleability of metals, in 
Malonic acid, 221 
Maltodextrin, 263 
Maltase, 298 
Maltose, 262 

Maltosazone (PI. VT, Fig. 2), 262 
Manganates, 64 
Manganese, 63 

compounds, 63 

hydroxide, 64 

reactions, 63 



Manganese, red lead test for, 63 

separation from zinc, 67 
Mannheim gold, 115 
Mannite, 206 
Marble, 71 

Marme's reagent, 428 
Marsh-Berzelius test for arsenic, 36 
Marsh gas, 200 

preparation of .(Exp. 63), 381 
Marsh's test for arsenic or antimony, 35 
Mass action, 8 

(defined), 1 
Mayer, A., on potassium sulphocyanates 

in saliva, Ref., 302 
McCauley, Dr., on copper in alloys, 
Ref, 123 

on zinc in alloys, Ref., 124 
McElhinney, Mark G, platinum 

solders, Ref., 133 
Measures, n 
Meerschaum, 74 
Meconic acid, 389, 417 
Mellot's metal, 128 
Melting-point of metals, in 

method of taking, 129 
Menthol, 181 
Mercaptan, 231 
Mercaptol, 231 
Mercuric bromide test for arsenic, 37 

chloride, 28, 181 

reaction with SnCl2, 29 

solution, 428 

sublimed (PI. I, Fig. 3), 106 

iodide, 29 

oxide, red, 28 

oxide, yellow, 28 
Mercurous chloride, 21 

iodide, 21 

nitrate, 21 

oxide, black, 22 
Mercury, 20 

alloys of, 21 

compounds of, 21 

excess of in amalgams, 125 

from mercuric oxide (PI. I, Fig. 5), 106 

in saliva, test for, 317 

properties of, 21 

reactions of, 22, 29 

recovery of , 142 

succinimide, 234 

tests for purity, 142 
Mesitylene, 246 
Metabolism, 361 
Meta-compounds (denned), 245 
Meta-cresol, 248 



INDEX 



447 



Metallic cement, Fletcher's, 30 

Metalloids, 16 

Metals, classification, 15, 16 

extraction of , 15 

group I, etc. (see Group) 

occurrence of, 15 

properties of , in, 112 

melting-points of , in 
Metaphosphate cement, 135 
Metaprotein, 284 

(denned), 274 

preparation of, 410 
Metastannic acid, 40 
Methane, 197, 200 
Methethyl, 181 
Methyl-alcohol, 206 

test for, 385 

-amine, 234 

-benzene, 245 

bromide, 203 

carbamine, 229 

carbinol, 207 

chloride, 182, 203 

chloroform, 203 
Methylene chloride, 203 

ether, 212 
Methyl ether, 212 

ethyl ether, 212 

hydrazine, 235 

indol, 234 

iodide, 203 

orange, 148 

oxide, 212 

salicylate, 250 

urea, 239 
Metric equivalents, 12 
Michaels, Dr. J. P., albumin in saliva, 

Ref., 298 
Michaels, Dr. J. P., methods of saliva 

analysis, Ref., 305 
Microchemical analysis, 168 
Microchemical methods, 169, 170 
Microscosmic salt, 87 
Microscope, use of, 168 
Milk, 281 

alcoholic fermentation, 284 

experiments with, 409 

fat, 284 

modified, 283 

of magnesia, titration of, 152 

plasma, 281 

reaction of, 281, 282 

specific gravity of, 281 

solids by calculation, 281 

wine, 284 



Miller, Dr. W. D., mucin in saliva, Ref., 

298 
Millon's reagent, preparation of, 428 

test (protein), 405 
Mineral oil, 199 
Mineral salts, metabolism, 366 
Minium, 23 
Mixed ether, 211 
Modified milk, 283 
Mohr's method of determination of 

arsenic, 157 
Moisture in teeth and tartar, 191 
Molar solution (defined), 144 
Molecules (defined), 2 
Molisch's reagent, 429 
Molisch's test for carbohydrates, 400 
Monobrom-methane, 203 
Monochlor-methane, 178 
Monosaccharides, 259 
Monoses, 260 
Monsel's salt, 54 
Morphine, 182 

(PI. Ill, Fig. 6), 171 

(microchemical test), 171, 172 

and Marine's reagent (PI. IV, Fig. 1), 
172 
Mosaic gold, 115 

Moth scales (PI. IX, Fig. 6), 353 
Mucic acid, 298 
Mucin, 280 

experiments with, 410 
(PI. IX, Fig. 5), 353 

from navel cord, 433 

in saliva, 297 

in urine, 358 
Mucoids, 274 
Murexide, note, 242 

test, uric acid (Exp. 131), 394 
Muscle, 289 

experiments with, 415 

plasma, 289 

serum, 289 
Musculin, 415 
Myogen, 415 
Myogenfibrin, 415 
Myosin, 289 

(Exp. 243c), 415 
Myosinfibrin, 415 
Myosinogen, 289, 415 

N. 
Naphtha, 200 
Natrium, 81 
Nephelometer, 296 
Nessler's reagent, 29, 429 



448 



INDEX 



Neutral salts, 5 
Nickel, 62 

alloys, 02 

borax bead, 63 

coin, 62 

plating, 62 

reactions of, 63 

separation from cobalt, 67 
Nirvanin, 182 
Niter, 79 
Nitrates, 100 
Nitric acid, dilute, 429 
Nitrils, 229 
Nitrites, detection of, 97 

in saliva, 303, 313 
Nitrobenzene, 248 

preparation of (Exp. 137), 395 
Nitrocellulose, 264 

Nitrogen, tests for in organic com- 
pounds, 194 
Nitroglycerine, 182 
Nitrous oxide, preparation of, 86 
Noble metals, 15 
Non-cohesive gold, 43 
Normal factor (defined) , 144 
Normal salt solution (physiological), 83 
Normal solution (defined), 143 
Novocaine, 183 
Nucleohistone, 274 
Nucleoproteins (defined), 274 

O. 

Occurrence of metals, 15 
Odontographic alloy, 125 
Oil of bitter almonds, 250 

cloves, 183 

gaultheria, test for, 183 

mirbane, 248 

wintergreen, 250 
Oils, 265 

experiments with, 403 
Olefin series of hydrocarbons, 202 
Oleic acid, 219, 266 
Optical analysis, sugar solution, 349 
Organic acids, 216 

chemistry, 193 

experiments with, 389-390 

matter in teeth and tartar, 191 
Orpiment, 32 

Ortho-compounds (defined), 245 
Orthocresol, 248 
Orthoform, 183 
Osazones, 261 
Osmosis, 10 

(Exp.), 369 



Osmotic pressure, 10 

Outline analysis, group I-V, 25, 51, 60, 

68,77 
Outline analysis of groups III-V, phos- 
phates present, 90 
Ovoglobulin, 273 
Oxalates, 95 , 99 

in urine, 356 
Oxalic acid, 220 

(sublimed) (PI. I, Fig. 1), 106 

natural sources of, 221 

standard solution of, 149 

in tartar, 190 

preparation of, 221 
Oxaluric acid, 239 
Oxidation of alcohols, 208 
Oxidases (see oxydases) 258 
Oxidation and reduction, analysis by, 

153 
Oxidation (Exp. 1, 2, 3), 367 
Oxyacids, 222 
Oxybenzene, 246 
Oxybutyric acid, 224 
Oxy chloride cements, 137 

of zinc, 137 
Oxydase in saliva, detection of, 314 
Oxydases, 258 

preparation of (Exp. 155), 398 

in saliva, 299 
Oxyhemoglobin, 288 
Oxyphosphate cement, 137 

of copper cement, 138 
zinc, 135 
Oxypropionic acid, 222 
Oxysulphate of zinc, 137 

P. 

Palmitin, 219 

note, experiment, 181 
Palmitic acid, 217, 219 

(Plate IV, Fig. 5), 172 

Pancreatic digestion, 321 

extract, 429 

juice, 321 

(Exp. 261), 421 

rennin, 322 
Parabanic acid, 239, 241 
Para compounds (defined), 245 
Para cresol, 248 
Para-acet-phenetidine, 249 
Paraffin, 199 

oil, 200 

series, 197 

wax, 199 
Paraform, 208 



INDEX 



449 



Paraformaldehyde, 208 
Paraglobulin (Exp. 202), 408 
Paralactic acid, 223 
Paraldehyde, 208 
Paramyosinogen, 289, 415 
Paris green, 27 
Pearl ash, 79 
Pearson's solution, 33 
Pentane, 197 
Pentoses, 259 
Pepsin, 319 

hydrochloric acid, 417 
Pepsinogen, 319 
Peptides, 275, 286 
Peptones, 275, 285 

experiment with, 411 
Permanganate, standardization of, 153 
Peroxidases, 258 

in saliva, 299 
Peroxide of calcium, 180 

hydrogen, 180 

preparation of (Exp. 17), 371 
strength of, 154 
titration by KMn0 4 , 154 
titration by Na2S 2 3 , 155, 156 

lead {see black oxide), 23 

sodium, 81, 180 

zinc, 180 
Petroleum jelly, 200 
Pewter, 40 
Phase (defined), 6 
Phenacetine, 249 
Phenol, 183, 246 

compound, 184 

difference from cresol, 177 

preparation of (Exp. 154), 398 

test for, 184 
Phenolphthalein, 148, 252 
Phenolphthalin, 299 
Phenol-sulphonic acid, 252 

preparation of, 429 
Phenyl-formamide, 235 

-glucosazone, 261 

-hydrazine, 236 

test for sugar, (Exp. 173), 401 
solution, 429 

-isocyanide, 229 

-salicylate, 250 
Phenol-sulphonic acid, 252 

-sulphuric acid, 252 
Phenyl-hydrazine test, 349, 401 
Phloroglucinol, 247 
Phosphates, 95, 98, 99 

as urinary sediment, 338 

determination in saliva, 312 



Phosphates, in saliva, 300 

metabolism of, 365 

in urine, 355 

of sodium, 83 

titration with uranium, 339 
Phospho-proteins (defined), 274 
Phosphoric acid, factor, 339 

in teeth and tartar, 192 

ionization of, 8 

titration with uranium nitrate, 339 
Phosphorus, test for, 195 
Phthalic acid, 252 

anhydride, 252 
Physical isomerism, 224 
Physiological chemistry, 256 

salt solution, 83 
Picric acid, 249 

solution, 429 
Pig iron, 53 
Pineapple essence, 215 
Piotrowski's test (Exp. 189), 406 
Pitchblende, 70 
Placer mining, 42 
Plaster compound, 73 

expansion of, 73 
Plaster of Paris, 72 

slabs, preparation of, 107 
Plate I, 106 

II, 170 

III, 171 

IV, 172 

V, 204 

VI, 262 

VII, 287 

VIII, 316 

IX, 353 
X,355 

Platinum, 45 

alloys, 46 

aluminium solder, 131 

amalgam, 123 

annealing of, 117 

black, 45 

color, for enamel, 46 

in dental alloy, 125 

reactions of, 46 

solder for, 133 
Polymers, 198 
Polyoses, 262 
Polysaccharides, 262 
Polysulphides, 80, 87 
Potash alum, 56 
Potassio-auric iodide, 45 
Potassio-mercuric iodide, 29 
Potassium, 78 



45° 



INDEX 



Potassium, antimony tartrate, 225 

bicarbonate, 79 

bi tartrate, 80, 225 

bromate, 79 

bromide, 79 

carbonate, 79 

chlorate, 80 

chloride (PI. VIII, Figs. 5, 6), 316 

compounds of, 78 

cyanate, 230 
preparation of, 434 

cyanide, 79, 228 
hydrolysis of, 229 (also Exp. 119) 

ethylate, 205 

ferricyanide, 230 

ferrocyanide, 229 
solution, 429 

hydroxide, 78, 184 

iodide, 79 

iodo-hydrargyrate, 29 

methylate, 205 

nitrate, 79 

permanganate, 63 

phenolate, 246 

platinic chloride, 47, 80 
(PI. Ill, Fig. 3), 171 

reactions of, 80 

salts of, 79, 80 

effect on metabolism, 364 

sulphide, 80 

sulphocyanate (thiocyanate) in saliva, 
301 

standard solution of, 160 
test for (Exp. 247), 417 
Potato spirit, 207 

starch (PI. VI, Fig. 6), 262 
Precipitation, n 
Primary alcohol, 206 

amines, 233 

ionization, 8 
Prinz, Dr. H., on phenol sulphonic acid, 

Ref., 253 
Proenzymes (denned), 257 
Prolamines, 277 

(denned), 273 
Propane, 197, 201 
Propenyl, 215 
Propionic acid, 218 
Propylene, 202 
Prosecretin, 324 
Protamines (denned), 273 
Proteans (defined), 274 
Protein (defined), 272 
Proteins, 269 

classification of, 269 



Proteins, color reactions of (Exp. 187- 
190), 405 

metabolism of, 363 

precipitants of (Exp. 191-195), 406 
Proteolytic enzymes in saliva, 299 
Proteoses, 285 

experiment with, 411 
Proteoses (denned), 275 
Prothero, Dr. J. H., Ref., 72 
Proto-albumose, 411 
Proximate analysis, 194 

principles, 194 
Prussian blue, 55 
Prussic acid, 228 
Pseudo-cellulose, 264 
Pseudo-nucleo-albumin, 283 
Ptomaines, 234 
Ptyalin {see also amylolytic enzymes) 

action on starch (Exp. 245), 416 

conditions affecting action of in saliva 
(Exp. 246), 298 
Purin, 240 

nucleus, 240 
Purple of Cassius, 45 
Pus (defined), 288 

urinary sediment, 357 

(PL IX, Fig. 3), 353 
Putrescin, 234 
Pyknometer (cut), 307 
Pyridin, 254 

Pyrocatechin (pyrocatechol), 246 
Pyrogallic acid, 247 
Pyrogallol, 247 
Pyrolusite, 63 
Pyrotartaric acid, 221 



Qualitative analysis, 15 

of dental alloys, 166 
Quantivalence, 4 
Questions on group I, 25 

group II, 51 

group III, 60 

group IV, 68 

group V, 77 

group VI, 88 
Questions on volumetric work, 167 
Quinalin, 254 

R. 

Racemic compounds, 225 

Radium, 70 

Reaction of saliva, 292 

Reactions, completed and reversible, 5 

Realgar, 32 






INDEX 



451 



Red blood corpuscles, 287 
Red lead, 23 

test for manganese, 63 
Red precipitate, 29 
Red prussiate of potassium, 230 
Reduced iron, 54 
Rees's alloy, 40 
Reinsch's test for arsenic, 34 
Renal casts, 357 

(PL IX, Fig. 4), 353 

epithelium, 356 
Rennin, 320 

(Exp. 253), 419 
Residue, recovery of gold, 141 

mercury, 142 

silver, 141 
Resorcinol, 247 
Reticulin, 278 
Reversible reactions, 5 
Rhigoline, 184, 200 
Rice starch (PL VI, Fig. V), 262 
Richmond, Dr. C. M., fusible alloy, 
128 

gold solder, 133 
Ringer's solution, 184 
Rochelle salts, 84, 225 
Rock oil, 199 
Rose's metal, 128 
Rose's reaction, 370 
Rule for changing C. to F. degrees, 
13 

S. 
Saccharic acid, 260 
Saccharin, 184 
Saccharin, test for, 184 
Saccharose, 262 
Salammoniac, 86 
Saleratus, 79, 82 
Salicylates, 250 
Salicylic acid, 25b 

test for (Exp. 153), 398 
Saliva, 291 

acetone in, 313 

acidity of, 293 

action on starch (Exp. 245), 416 

albumin in, 314 

alkalinity of, 292, 319 

ammonium salts in, 301 

analysis blank and use, 360 

analysis of, 304 

carbon dioxide in, 293 

color of, 296 

constituents of, 297 

determination of ammonia, 310 



Saliva, determination of ash, 315 
of chlorides, 311 
of nitrites, 313 
of phosphates, 312 
of potassium sulpho-cyanate, 308 
of solids, 315 
of specific gravity, 308 

determination of urea, 311 

dialyzed, 316 

enzymes in, 313, 314 

experiments with, 416 

glycogen in, 312 

lactic acid in, 317 

mucin in, 297, 314 

nitrates in, 303 

nitrites in, 303 

odor of, 297 

oxydase, detection of, 314 

physical properties of, 292, 305 

ptyalin in, 298 

quantity of, 292 

reaction, 292, 307 

specific gravity, 292 

sulphocyanates in, 302 

variation in composition, 291 

viscosity of, 305 
Salivary sediment, 318 
Salmine, 274 
Salol, 250 
Sal soda, 81 
Salt (defined), 4 
Salt of sorrel, 221 
Saltpeter, 79 
Salts in metabolism, 364 
Salts of tartar, 79 
Salt solution, decinormal, 159 
Salvarsan, 249 

Sanger & Black (Gutzeit's test), Ref., 37 
Saponification (Exp. 182), 403 
Sarcolactic acid, 223 
Saturated hydrocarbons, 199 
Scale salts of iron, 225 
Schiff's reagent, 429 
Scombrone, 273 
Secondary alcohol, 206 

amines, 234 
Secondary protein derivatives, 275 
Secretin, 323 
Sediment in saliva, 318 
Sediment in urine, 353 
Semipermeable membrane, 10 
Serum albumin, 286, 275, 276 

blood, 286 

globulin, 286 
Sidenite, 53 



452 



INDEX 



Silver, 18 

alloys, 19 

alloy, 60 per cent, 125 

amalgam, 123 

decinormal solution of, 159 

fire assay, 165 

glance, 18 

gravimetric determination of, 164 

hydroxide, 19 

in dental alloy, determination of, 
160 

nitrate, 185 
solutions, 430 

oxide, 19 

platinum alloy, 19 

properties of, 18 

reactions, 20 

recovery of, 141 

solder for, 133 

stains, removal of, 19 

thiosulphate, 19 

tin alloys, 123 

titration of by KCNS, 160 
by NaCl, 160 
Silvering mirror (alloy used), 40 
Simple ethers, 211 

proteins, 272, 275, 278 
Skatol, 254 

Skatoxyl potassium sulphate, 254 
Small calorie (denned), 362 
Smaltite, 61 
Smelling salts, 85 
Smithsonite, 64 
Smoky urine, 328 
Soap, 267 
Soapstone, 74 
Sodium, 81 

acid urate (PL X, Fig. 3), 355 

amalgams, 121 

bicarbonate, 82 

carbonate, 81 

chloride, 83, 185 

$ per cent. (PL VIII, Fig. 2), 316 
decinormal solution, 159 
effect on metabolism, 364 

compounds, 81 

hydroxide, 81 
decinormal, 150 

nitrate, 83 

oxalate in urine, 356 

microchemical crystals, 171 
(PL II, Fig. 4), 170 

perborate, 180, 185 

test for H2O2 (Exp. 20), 372 

peroxide, 81, 180, 185 



Sodium, phosphates, 83 
and uric acid, 242 

potassium tartrate, 84 

pyroantimonate, 84 

reaction of, 84 

stannate, 41 
Sodium stannite preparation, 31, 41 

tetraborate, 176 

thiosulphate N/10 solution, 155 

uranyl acetate, 84 

urate, in urine, 355 
microchemical crystals, 171 
(PL X, Fig. 3), 355 

zincate, 65 
Soft solder, 129, 130 
Solder, 129 

for aluminium, 130, 131 

for brass, 131 

for gold, 131 

for platinum, 133 

for silver, 133 
Soldering acid, 130 
Solids in saliva, 315 
Solid solution, 117 
Solubility tables, 91, 92 
Soluble anhydrite, 72 

cotton, 264 
Solution explained, 9 
Solvate theory, H. C. Jones, 9 
Solvay process, 82 
Somnoform, 1-85 
Spathic iron ore, 53 
Specific gravity, 13 

of amalgams, 127 

of saliva, 292 

determination of, 308 
Spence, Dr. S. J., expansion of plaster, 

Ref., 73 
Spermatozoa, 358 

(PL IX, Fig. 2), 353 
Sperrylite, 45 
Spirit of Mindererus, 86 
Sputum, 297 
Standard alloy, 125 

dental alloy, 125 

solutions, 143 
Stannous chloride, 41 
Stannum, 40 
Starch, 262 

experiments with, 402 

hydrolysis of (Exp. 245), 416 

hydrolytic products of, 263 

paste (Exp. 178), 402 

preparation (Exp. 177), 402 
Steapsin, 322 









INDEX 



453 



Stearic acid, 217, 219 

digestion of, 363 
Stearopten, 265 
Steel, 53 

carbon in, 53 
Stereo-isomerism, 224 
Sterling silver, 19, 115 
Stibium, 38 
Stibnite, 38 

Stiles, Dr. Percy G., Ref., on metab- 
olism, 363 
Stoke's reagent, note, 413 
Stomach steapsin, 320 
Stovaine, 186 

and Pt2CLj (microchemical test), 172 
(PL IV, Fig. 4), 172 
Straight chain hydrocarbons, 198 
Stroma of blood corpuscles, 287 
Strontium, 71 

oxalate (m. a), 171 
(PI. II, Fig. 3), 170 

reactions of, 71 

salts and flame test, 71 
Strontianite, 71 
Sturine, 274 

Substituted ammonias, 233 
Substitution products of the hydrocar- 
bons, 196 
Succinic acid, 221 

natural sources of, 221 
Succinimide, 234 
Sucrose, 262 
Sugar in saliva, 300 

in urine, 346 

of lead, 23 

quantitative determination by 
Fehling's solution, 347 

quantitative determination by fer- 
mentation, 349 
Sugars, 259 

tests for (Exp. 167, etc.), 400 
Sulphanilic acid, 252 
Sulphates, 95, 98 

in urine, 340 
Sulphides, determination of, 93, 95, 97 
Sulphites, test for, 94 
Sulphocyanates in saliva, 301, 302, 308 

test for, 96 
Sulphocyanic acid, 230 
Sulphonol, 231 
Sulphones, 231 
Sulphonic acids, 232 
Sulphur compounds (organic), 231 

tests for, 195 

total in urine, determination, 340 



Sulphuret of potassium, 80 

Sulphuric acid, dilute, 430 

Sulphuric ether, 212 

Sulphur iodides (for blow pipe test), 107 

Suprarenal glands, 186 

Suprarenalin, 174 

Sweet spirits of niter, 214 

Sylvanite, 42 

Sylvite, 78 

Symbols (denned), 3 

Symmetrical hydrocarbons, 246 

Syntonin, 276, 285 



Talcum, 74 
Tannic acid, 186, 251 
Tannin, 186 
Tartar, 189 

composition of, 190 

crude, 80 

emetic, 39, 225 
Tartaric acid, 224 
Taurine, 232 

Taurocholic acid in bile, 323 
Teeth, analysis of, 191 
Teeth and tartar, 189 
Teichmann's hemin crystals, 289 

(PI. VII, Fig. 2), 287 

test (Exp. 239), 414 
Temporary alloy, 125 
Terpenes, 267 
Tertiary alcohols, 206 
Thein, 241 
Thermometers, 12 
Thioalcohol, 231 

Thiocyanate in saliva, determination, 
308 

test for, 96 
Thiocyanic acid, 230 
Thioethers, 231 
Thioketones, 231 
Thiosulphates, test for, 94, 97 
Thorner, on acidity of milk, Ref., 282 
Thrombase, 286 
Thrombin, 286 
Thymol, 186, 247 

iodide, 186 
Thymophen, 187 
Thyroids, 187 
Tin, 40 

alloys, 40 

amalgams, 123 

cement, 138 

chloride, preparation of, 41 

reaction with HgCl 2 , 29 



454 



INDEX 



Tin, compounds of, 40 

gravimetric determination of, 163 

nitric acid, reaction with, 41 
reactions of, 41 
Tincture of iodine for reagent, 430 
Tinstone, 40 
Titration (denned), 150 
Tollen's reagent (Exp. 85), 386 

preparation, 430 

test for aldehyde (Exp. 85), 386 
Toluene, 245 
Toluol, 245 

Tribrom-methane, 203 
Tribrom-phenol, 184 

(M. C), 171; also (Exp. 143), 396 

(PL III, Fig. 5), 171 
Trichloracetic acid, 187 
Trichloraldehyde, 208 
Trichlormethane, 176, 203 
Tricresol, 248 
Trihydroxybenzene, 247 
Tri-iodomethane, 204 
Trimethylamine, 233, 234 
Trimethylbenzene, 246 
Trinitro cellulose, 264 

phenol, 249 

preparation (Exp. 147), 397 
Triolein, 266 
Trioxymethylene, 208 
Trioxypurin, 240 
Tripalmitin, 266 
Triple-bonded hydrocarbons, 202 

phosphates, 355 
Tristearin, 266 
Tritenyl, 215 
Tropa-cocaine, 187 
Tropceolin (Exp. 253d), 420 

solution, 430 
Truedentalloy, 125 
Trypsin, 321 
Trypsinogen, 321 
Twentieth Century alloy, 125 
Type metal, 115 
Tyrosin, 227, 251 

preparation, 434 

(PI. V, Fig. 6), 204 

U. 

Uffelmann's reagent (Exp. 257), 420 

preparation of, 430 
Ultimate analysis, 194 
Unsaturated hydrocarbons, 201 
Unsymmetrical hydrocarbons (denned) , 

246 
Uraninite, 70 



Uranium, standard solution of, 339 
Uranyl sodium acetate, 84 
Urates in urine, 355 
Urea, 237, 238 

and NaBrO (reactions), 238 

and H2O (reactions), 237 
Urea determined by Doremus Hinds 
apparatus, 333 

by Ferris' apparatus (saliva), 311 

by Squibb 's apparatus, 332 

determination of, 311 

experiments with, 394 

in saliva, 300 

nitrate, 238 

(PL V, Fig. 3), 204 

oxalate, 238 
(M. C), 171 
(PL II, Fig. 5), 170 

qualitative test for, 331 
Urea (synthesis of Exp. 126), 393, 434 
Ureas, substituted, 239 
Urease, 258 
Ureides (denned), 239 
Uric acid, 210, 241, 334 

(PL X, Fig. 1 and 2), 355 

and lithium salts, 242 

and Na2HP04, 242 

determination, 334 
Cook's method, 334 
Folin's method, 335 
Hopkin's method, 335 

murexide test for, 394 

proportion to urea, 355 

in urinary sediments, 354 
Urinary sediments, 353 
Urine, 326 
Urine, abnormal constituents, 343 

acetone in, 350 

acidity of, 329 

albumin in, 343 

alkaline phosphates in, 337 

ammonia in, 335 

analysis blank and use, 359 

appearance of, 328 

bile in, 351 

brick dust deposit in, 241 

causes of cloudy, 328 

chlorine in, 337 

color of, 327 

coloring matter in, 341 

epithelium in, 356 

indoxyl in, 341 

method of collecting, 327 

normal solids in, 331 

phosphates in, 337 



INDEX 



455 



Urine, estimation of, 338, 339 

physical properties of, 327 

quantity, 327 

reaction, 329 

soluble salts in, 341 

specific gravity, 329 

sulphates, 340 
Urinometer, 329 
Urobilin, 341 
Urochrome, 341 
Uroerythrin, 341 
Urorosein, 341 

V. 

Valence (defined), 3 
Valeric acid, 218 
Vaseline, 200 
Vegetable globulin, 434 
Vegetables, oxalic acid in, 221 
Verdigris, 27 
Vinegar, 217 

determination of strength, 151 
test for malic acid (Exp. 113), 391 
Viscosity of saliva, 305 
Vitamines, 366 
Vitellin, 274 
Volatile alkali, 87 

oils, 267 
Volumetric analysis, 143 
Von Eckart's alloy, 19 

W. 

Washing soda, 81 

Water, detection of in alcohol (Exp. 75), 

.384 
Weights and measures, 1 1 
Weldon's process for chlorine, 63 
Wheat starch (PL VI, Fig. 4), 262 
White arsenic, 32 

blood corpuscles, 287 

copper cement, 138 

lead, 23 

precipitate, 28, 29 

vitriol, 65 
Will & Varrentrap's test for nitrogen, 

i95 
Wilson, Dr. G. H., expansion of plaster, 

Ref., 72 
Witherite, 70 

Wohler's test for nitrogen, 195 
Wood's metal, 128 



Wood spirit, 206 
Wool fibers (PI. IX, Fig. 6), 353 
Wrought iron, 53 
carbon in, 53 

X. 

Xanthin, 240 

Xanthroproteic test (Exp. 187), 405 

Xylene, 245 

Xylol, 245 

Xylose, 259 

Y. 

Yeast, 256 

cells and molds (PI. X, Fig. 4), 355 
Yellow prussiate of potassium, 229 
Yellow wash, 28 

Z. 

Zein, 277 
Zinc, 64 
Zincates, 65, 66 
Zinc alloys, 65 
• amalgams, 123 

blende, 64 

carbonate, 64, 65 

compounds, 65 

ferrocyanide, 66 

gold solder, 131 

gravimetric determination of, 165 

hydrate, 65 

in amalgam alloys, 65 

in dental alloys, 124 

lactate, 224 

melting point, 64 

oxalate, 66 

(PI. II, Fig. 6), 170 

oxide, preparation of, 136 

oxychloride, 137 

oxyphosphate, 135 

oxysulphate, 137 

peroxide, 180 

properties of, 64 

reactions of, 65 

sarcolactate, 223 

separation from manganese, 67 

sulphate, 65 

sulphide, 65 

volumetric determination of, 162 

white, 65 
Zymase, 258 
Zymogens, 257 



TABLE OF ATOMIC WEIGHTS (1917) 



Aluminium 


Al 


27.1 


Molybdenum 


.Mo 


96.0 


Antimony 


Sb 


120.2 


Neodymium 


.Nd 


144.3 


Argon 


A 


39.88 


Neon 


.Ne 


20.2 


Arsenic 


As 


74.96 


Nickel 


.Ni 


58.68 


Barium 


Ba 


137.37 


Niton (radium emanation) 


.Nt 


222.4 


Bismuth 


Bi 


208.0 


Nitrogen 


.N 


14.01 


Boron 


B 


11.0 


Osmium 


.Os 


190.9 


Bromine 


Br 


79.92 


Oxygen 


.0 


16.00 


Cadmium. . 


Cd 


112.40 


Palladium 


.Pd 


106.7 


Caesium 


Cs 


132.81 


Phosphorus 


P 


31.04 


Calcium 


Ca 


40.07 


Platinum 


.Pt 


195.2 


Carbon 


C 


12.005 


Potassium 


K 


39.10 


Cerium 


Ce 


140.25 


Praseodymium 


.Pr 


140.9 


Chlorine 


CI 


35.46 


Radium 


.Ra 


226.0 


Chromium 


Cr 


52.0 


Rhodium 


.Rh 


102.9 


Cobalt 


Co 


58.97 


Rubidium 


.Rb 


85.45 


Columbium 


Cb 


93.1 


Ruthenium 


.Ru 


101.7 


Copper 


Cu 


63.57 


Samarium 


.Sa 


150.4 


Dysprosium 


Dy 


162.5 


Scandium 


.So 


44.1 


Erbium 


Er 


167.7 


Selenium 


.Se 


79.2 


Europium 


Eu 


152.0 


Silicon 


.Si 


28.3 


Fluorine 


F 


19.0 


Silver 


• Ag 


107.88 


Gadolinium 


Gd 


157.3 


Sodium 


.Na 


23.00 


Gallium 


Ga 


69.9 


Strontium 


.Sr 


87.63 


Germanium 


Ge 


72.5 


Sulfur 


.S 


32.06 


Glucinium 


Gl 


9.1 


Tantalum 


.Ta 


181.5 


Gold 


Au 


197.2 


Tellurium 


.Te 


127.5 


Helium 


He 


4.00 


Terbium 


.Tb 


159.2 


Holmium 


Ho 


163.5 


Thallium 


.Tl 


204.0 


Hydrogen . 


H 


1.008 


Thorium 


.Th 


232.4 


Indium 


In 


114.8 


Thulium 


.Tm 168.5 


Iodine 


I 


126.92 


Tin 


.Sn 


118.7 


Iridium 


Ir 


193.1 


Titanium 


.Ti 


48.1 


Iron 


Fe 


55.84 


Tungsten 


.W 


184.0 


Krypton 


Kr 


82.92 


Uranium 


.U 


238.2 


Lanthanum 


La 


139.0 


Vanadium 


.V 


51.0 


Lead 


...... Pb 


207.20 


Xenon 


.Xe 


130.2 


Lithium 


Li 


6.94 


Ytterbium (Neoytterbium) 


.Yb 


173.5 


Lutecium 


Lu 


175.0 


Yttrium 


.Yt 


88.7 


Magnesium 


Mg 


24.32 


Zinc 


.Zn 


65.37 


Manganese 


Mn 


54.93 


Zirconium 


.Zr 


90.6 


Mercury 


Hg 


200.6 









